UNIT 12
ELECTROSTATICS
Q.1. Define
Electrostatics and Electric Force. 12112001
Q.2 (a) State and explain Coulomb’s law. Express the
law in vector form. 12112002
(b) What is the effect of the medium on
Coulomb’s force?
Q.3 What
do you know about fields of force? 12112003
Q.4 What
do you know about electric intensity or electric field intensity? 12112004
Q. 5.
Find electric field intensity at a point due to a point charge q placed at a
distance r from it.
Q.6 What
are electric field lines? Also write down their characteristics. 12112006
Q.7 What
is xerography? Write down construction and working of a photocopier. 12112007
Q.8 What
is inkjet printer? How does it work? 12112008
Q.9 Explain
the term electric flux. 12112009
Q.10 Find
electric flux through a closed surface enclosing a point charge. 12112010
Q.11 State
and explain Gauss’s law. (Board 2015,
16) 12112011
Q.12 Find
the Electric field intensity inside the hollow charge conductor. 12112012
Q.13Find the Electric field intensity at a
point very infinite sheet of charge.(Board 2014)12112013
Q.14 Find
the field intensity between oppositely charged metal plates. 12112014
Q.15 What
is meant by the term potential difference? 12112015
Q.16 Establish
a relationship between electric potential and electric intensity. 12112016
OR
Prove that E
= 
Q.17 (a) Define electrical potential. 12112017
(b) Determine electric potential at a point due to
point charge. (Board 2013, 14, 15)
Q.18 Define
electron volt and relate it to joule. 12112018
Q.19 Make
a comparison between electric and gravitational forces. 12112019
Q.20 How
did Millikan measure charge on an electron? (Board 2013) 12112020
Q.21 What
is meant by a capacitor and its capacitance? Find an expression for the
capacitance
of parallel plate capacitor. 12112021
Q.22 Explain
electric polarization. How does it affect capacitance? 12112022
Q.23 How
is energy stored in a capacitor? Derive an expression for energy. 12112023
Q.24 Describe
charging and discharging of a capacitor. 12112024
Charging
a Capacitor:
SHORT
QUESTIONS
Q.1 The
potential is constant throughout a given region of space. Is the electrical
field zero or non-zero in this region? Explain. 12112025
Q.2 Suppose that you follow an electric field line
due to a positive point charge.
Do electric field and the potential increase or decrease? (Board 2014,16) 12112026
Q.3 How can you
identify that which plate of a capacitor is positively charged?
(Board 2013) 12112027
Q.4 Describe the force or forces on a positive
point charge when placed between parallel plates. (Board 2015,16) 12112028
(A) with similar and equal charges
(B) with opposite and equal charges
Q.5 Electric lines of force never
cross. Why? (Board 2010, 13, 15) 12112029
Q.6 If a point charge q of mass m
is released in a non-uniform electric field. Will it make a rectilinear motion?
(Board 2014)12112030
Q.7 Is
E necessarily zero inside a charge rubber balloon if balloon is spherical?
Assume that charge is distributed uniformly over the surface. (Board 2010,
14) 12112031
Q.8 Is it true that Gauss’s law
states that the total number of lines of force crossing any closed surface in
the outward direction is proportional to the net positive charge enclosed
within surface? 12112032
Q.9 Do electrons tend to go to
region of high potential or of low potential?
(Board 2013, 14, 16) 12112033
Solved Examples
Example 1: 12112034
Charges
and 
are located in xy-plane at positions 
and 
respectively. Where the distances are measured
in metres. Calculate the force on 
. (Fig. 12.3)
Example 2: 12112035 Two positive point charges q1
= 16.0 mC and q2
= 4.0 mC are separated by
a distance of 3.0 m, as shown in Fig. 12.5. Find the spot on the line joining
the two charges where electric field is zero.
Example 3: 12112036
Two
opposite point charges, each of magnitude q are separated by a distance 2d.
What is the electric potential at a point P mid-way between them?
Example 4: 12112037
A
particle carrying a charge of 2e falls through a potential difference of 3.0V.
Calculate the energy acquired by it.
Example 5: 12112038
In Millikan oil drop experiment, an oil drop of mass 4.9´10-15kg
is balanced and held stationary by the electric field between two parallel
plates. If the potential difference between the plates is 750V and the spacing
between them is 5.0mm, calculate the charge on the droplet.
Assume g =
9.8ms-2.
Example 6: 12112039
The
time constant of a series RC circuit is t = RC. Verify that an ohm times farad
is equivalent to second.
PROBLEMS
Q.1 Compare
magnitudes of electrical and gravitational force exerted on an object (mass =
10.0g, charge = 20.0mC) by
an identical object that is placed 10.0cm from thefirst. (G = 6.67 ´ 10-11 Nm2 kg-2)
Ans. 12112040
Q.2 Calculate
vectorially the net electrostatic force on q as shown in the fig.
Data: 12112041
Q.3 A
point charge q = -8.0 ´ 10-8
C is paced at the origin. Calculate electric field at a point 2.0m from the origin on the z-axis. 12112042
Q.4 Determine
the electric field at the position r = 
caused by a
point charge q = 5.0 ´ 10-6C
placed at origin.
Data: 12112043
Q.5 Two point charges, q1 = -1.0 ´
10-6C and q2 = +4.0 ´
10-6C, are separated by a distance of
3.0m. Find and justify the zero-field location. 12112044
Q.6 Find the electric field strength required to hold suspended a particle
of mass1.0 x 10-6 kg and charge 1mc
between two plats 10.0cm apart. 12112045
Q.7 A
particle having a charge of 20 electrons on it falls through a potential
difference of 100 volts. Calculate the energy acquired by it in electron volts
(eV). 12112046
Q.8 In Millikan’s experiment, oil droplets are
introduced into the space between two flat horizontal plates, 500 mm apart. The
plate voltage is adjusted to exactly 780V so that the droplet is held
stationary. The plate voltage is switched off and the selected droplet is
observed to fall a measured distance of 1.50 mm in 11.2 s. Given that the
density of the oil used is 900kgm-3, and the viscosity of air at
laboratory temperature is 1.80´10-5
Nm-2s, calculate:
(a) the mass, and 12112047
Q.9 A proton placed in uniform electric field of
5000 NC-1 directed to right is allowed to go a distance of 10.0 cm
from A to B. Calculate: 12112048
(a) Potential difference between the two points
(b) Work done by the field
(c) The change in P.E. of proton
(d) The change in K.E. of the proton
(e) Its velocity (mass of proton is
0.67 ´
10-27 kg) 12112049
Q.10 Using zero reference point at infinity,
determine the amount by which a point charge
of 4.0 ´ 10-8 C alters
the electric potential at a point 1.2 m away, when 12112050
Q.11 In Bohr’s
atomic model of hydrogen atom, the electron is in an orbit around the nuclear
proton at a distance of 5.29 ´ 10-11 m with a speed of 2.18 ´ 106 ms-1.
Find 12112051
(a) The electric potential that a proton exerts at
this distance.
(b) Total energy of the atom in eV.
(c) The ionization energy for the atom in eV.
Data:
r = 5.29
´
10-11 m
v = 2.18
´
106 ms-1
e = 1.6
´
10-19 C
m = 9.1
´
10-31 kg
(a) Electric
potential=V=?
(b) Total
energy is eV=En=?
(c) Ionization
energy in eV=?
Q.12 The electronic flash attachment for a camera
contains a capacitor for storing the energy used to produce the flash. In one
such unit, the potential difference between the plates of a 750 mF capacitor is 330 V. Determine the energy that is used
to produce the flash. (Board 2015) 12112052
Q.13 A capacitor has a capacitance of 2.5 ´ 10-8 F. In the charging process, electrons
are removed from one plate and placed on the other one. When the potential difference
between the plates is 450 V, how many electrons have been transferred?
(e=1.60 ´
10-19 C) 12112053
UNIT 13
CURRENT ELECTRICITY
Q.1 (a) Define
electric current and its unit. (b) Explain the term conventional current. 12113001
Q.2 Describe current through metallic conductor. 12113002
Q.3 Explain the term drift
velocity. 12113003
Q.4 Describe
different sources of current. 12113004
Q.5 Discuss different effects of current. 12113005
Q.6 State and explain Ohm’s law. 12113006
Q.7 Describe the Series and
Parallel combination of Resistors. (Board 2010) 12113007
Q.8 What is
resistivity? Describe effect of temperature upon resistivity.(Board 2009) 12113008
Q.9 Describe the colour code scheme for carbon
resistances. 12113009
Q.10 What is a
Rheostat? How does it work as 12113010
(a) variable resistor
(b) potential divider? (Board 2014)
Q.11 What is thermistors? 12113011
Q.12 Determine
electrical power of a source. How does power dissipate in resistors?
(Board 2010)12113012
Q.13 What is meant by electromotive force? Derive
an expression for emf of a source. Also differentiate electromotive force and
potential difference. (Board 2013, 14) 12113013
Q.14 Determine maximum power output delivered to
the load resistance. 12113014
Q.15 Explain Kirchhoff’s rules. (Board 2015) 12113015
Q.16 What is Wheatstone Bridge? Give its
construction and derive balance condition by
applying Kirchhoff’s 2nd rule. (Board 2015) 12113016
Q.17 What is potentiometer? Give its
construction, theory and uses. (Board 2015) 12113017
SHORT QUESTIONS
13.1 A
potential difference is applied across the ends of a copper wire. What is the
effect on the drift velocity of free electrons by 12113018
(i) Increasing
the potential difference.
(ii) Decreasing the length and the temperature of the
wire. (Board 2016)
Ans.
13.2 Do
bends in a wire affect its electrical resistance? Explain.
(Board 2013, 14, 15, 16) 12113019
13.3 What
are the resistances of the resistors given in the figures A & B? What is
the tolerance of each? Explain what is meant by the tolerance? 12113020
13.4 Why does the resistance of a conductor rise with temperature?
(B 2010, 2013, 2016) 12113021
13.5 What
are the difficulties in testing whether the filament of a lighted bulb obeys
Ohm’s law? (Board 2014, 15, 16) 12113022
13.6 Is
the filament resistance lower or higher in a 500 W, 220 V light bulb than in a
100 W, 220 bulb? (Board 2013, 14) 12113023
13.7 Describe
a circuit which will give a continuously varying potential. 12113024
13.9 What
is Wheatstone bridge? How can it be used to determine an unknown
resistance? (Board 2015) 12113026
Solved Examples
Example 1: 12113027
1.0 ´ 107
electrons pass through a conductor in 1.0 ms. Find the current in
ampere flowing through the conductor. Electronic charge is 1.6´10-19C.
Example 2: 12113028
0.75A
current flows through an iron wire when a battery of 1.5V is connected across
its ends. The length of the wire is 5.0m and its cross sectional area is 2.5´10-7m2.
Compute the resistivity of iron.
Example 3: 12113029
A platinum wire has resistance of 10W at 0oC
and 20W
at 273oC. Find the value of temperature coefficient of resistance of
platinum.
Example 4: 12113030
The potential difference between the terminals of a battery in
open circuit is 2.2V. When it is connected across a resistance of 5.0W. The
potential falls to 1.8V. Calculate the current and the internal resistance of
the battery.
Example 6: 12113031
Calculate
the currents in the three resistances of the circuit shown in Fig.
PROBLEMS
13.1 How
many electrons pass through an electric bulb in one minute if the 300 mA
current is passing through it?
(Board
2015) 12113032
13.2 A charge of 90 C passes through a wire in 1
hour and 15 minutes. What is the current in the wire? (Board 2013, 14) 12113033
13.3 Find
the equivalent resistance of the circuit, total current drawn from the source
and the current through each resistor. 12113034
Data:
R1 = 6 W
R2 = 6 W
R3 = 3 W
E =
6 Volt
Re= ?
I1=
?
I2=
?
I3= ?
13.4 A rectangular bar of iron is 2.0 cm by 2.0
cm in cross section and 40 cm long. Calculate its resistance if the resistivity
of iron is 11 ´ 10-8Wm.(Board2009, 13, 14)
Data: 12113035
A = 2 ´
2 = 4 cm2 = 4 ´ 10-4 m2
L = 40 cm = 0.4m
r
= 11 ´
10-8W
m
R =?
13.5 The
resistance of an iron wire at 0oC is 1 ´104W.
What is the resistance at
500o C if the temperature coefficient of resistance of iron is 5.2 ´ 10-3
K-1? 12113036
Data:
Ro = 1 ´ 104W
Initial
temperature ti = O° C = 273 K
Final
temperature t2 = 500° C = 773 K
Increase in
temperature t = t2 - ti = 773 - 273
= 500 K
a
= 5.2 ´
10-3 K-1
Rt =?
13.6Calculate
terminal potential difference of each of cells in circuit of fig. 12113037
Data:
E1 = 24V
E2 = 6V
r1=0.1W
r2 = 0.9W
R= 8.0W
V1=?
V2=?
13.7 Find
the current which flows in all the resistances of the circuit of Fig. 12113038
Data:
E1 = 9.0 V
E2
= 6 V
R1 = 18 W
R2 = 12 W
Current through R1= ?
Current through R2= ?
13.8 Find
the current and power dissipated in each resistance of the circuit, shown in
fig. 12113039
Data:
R1 = 1W, R2 = 18W,
R3 = 1W, R4 = 1W,R5
= 2W
E1 = 6V, E2 = 10V
Current through R1= ?
Current through R2= ?
Current through R3= ?
Current through R4= ?
Current through R5= ?
Power dissipated in each resistor = ?
UNIT 14
ELECTROMAGNETISM
Q.1 Explain the production of magnetic field
due to current in a long straight wire
(In a straight conductor). (Board 2014) 12114001
Q.2 Derive formula for a force acting on a current carrying conductor,
placed inside uniform magnetic field. 12114002
Q.3 Define magnetic flux and magnetic flux density. (B 2013) 12114003
Q.4 State Ampere’s law. Using this law determine magnetic flux density
at any point inside a current carrying solenoid. (Board 2015) 12114004
Q.5 Derive
formula for the magnetic force on a moving electric charge in a magnetic field?
Ans: Force on a moving charge
in magnetic field: (Board 2015) 12114005
Q.6 Discuss motion of charged particle inside electric and magnetic
field. 12114006
Q.7 Determine e/m of an electron. (Board 2016) 12114007
Q.8 Write down construction working and uses of cathode ray
oscilloscope. 12114008
Q.9 Find torque in a current carrying coil. 12114009
Q.10 (a)Describe principle, construction &
working of a moving coil galvanometer. 12114010
(b) Narrate
the methods commonly used for observing the deflection.
(c)
How can a galvanometer be made more sensitive? (Board 2010)
Q.11 What is an ammeter? How can a galvanometer be used as an ammeter? 12114011
(Board 2013,
14)
Q.12 What is a voltmeter? How does a galvanometer converted into
voltmeter? 12114012
(Board 2013)
Q.13 What is Avo-meter? Draw its block diagram and discuss its various
functions. 12114013
Q.14 What is digital Multimeter. 12114014
SHORT QUESTIONS
14.1 A plane conducting loop
is located in a uniform magnetic field that is directed along the x-axis. For
what orientation of the loop is the flux maximum, for what orientation is the
flux a minimum? 12114015
14.2 A current in a conductor
produces a magnetic field which can be calculated using Ampere’s law. Since
current is defined as the rate of flow of charge, what can you conclude about
the magnetic field due to stationary charges, what about moving charges? 12114016
14.3 Describe the change in
the magnetic field inside a solenoid carrying a steady current I, if length of
solenoid is doubled but no. of turn remains the same. Similarly, if no. of
turns are doubled but the length remain the same. 12114017
14.4 At a given instant, a
proton moves in the positive X-direction in a region where there is magnetic
field in the negative z direction. What is the direction of the magnetic force?
Will the proton continue to move in the positive X-direction? Explain? 12114018
14.5 Two charged particles are
projected into a region. Where there is a magnetic field perpendicular to their
velocities. If the charges are deflected in opposite directions, what can you
say about them? (Board 2015) 12114019
14.6 Suppose that a charge q is moving in a
uniform magnetic field with a velocity V. Why is there no work done by the
magnetic force that acts on the charge q?
12114020
14.7 If a charge particle
moves in straight line through some region of space, can you say that the
magnetic filed in the region is zero? 12114021
14.8 Why does the picture on a TV
screen become distorted when a magnet is brought near the screen? (Board 2010, 13, 15) 12114022
14.9 Is it possible to orient
a current loop in a uniform magnetic field, such that the loop will not tend to
rotate? Explain.
(Board 2010, 16 ) 12114023
14.10 How can a current loop be
used to determine the presence of a magnetic field in a given region of space?(Board 2014,
16)
12114024
14.11 How can you use a magnetic
field to separate isotopes of chemical element?
(Board 2013,
14, 15) 12114025
14.12 What should be the orientation of a current
carrying coil in a magnetic field so that torque acting upon the coil is (a)
maximum (b) minimum? (Board 2014, 16)
12114026
14.13 A loop of wire is
suspended between the poles of a magnet with its plane parallel to the pole
faces. What happens if a direct current is put through the coil? What happens
if an alternating current is used instead? 12114027
14.14 Why the resistance of
ammeter should be very small?
(Board2010,13, 15) 12114028
14.15 Why a voltmeter should
have very high resistance? (Board 2013,
15, 16) 12114029
Solved Examples
Example 1: 12114030
A 20.0cm
wire carrying a current of 10.0A is placed in a uniform magnetic field of
0.30T. If the wire makes an angle of 40o with the direction of
magnetic field, find the magnitude of the force acting on the wire.
Example 2: 12114031
The magnetic
field in a certain region is given by
. How much flux passes through a 5.0cm2 area loop
in this region if the loop lies flat in the xy-plane?
Example 3: 12114032
A
solenoid 15.0cm long has 300 turns of wire. A current of 5.0A flows through it.
What is the magnitude of magnetic field inside the solenoid?
Example 4: 12114033
Find the radius of an orbit
of an electron moving at a rate of 2.0´107ms-1 in a uniform
magnetic field of 1.20´10-3T.
Example 5: 12114034
Alpha particles ranging in speed from 1000ms-1
to 2000ms-1
enter into a velocity selector where the electric intensity is 300Vm-1 and the magnetic
induction 0.20T. Which particle will move undeviated through the field?
Example 6: 12114035
What shunt resistance must be connected across a galvanometer of 50.0W resistance which gives full scale deflection with 2.0mA
current, so as to convert it into an ammeter of range 10.0A?
PROBLEMS
14.1 Find the value of the magnetic field that
will cause a maximum force of
7.0 ´ 10-3 N on a
20.0cm straight wire carrying current of 10.0A?(Board 2014)
F
= 7.0 x 10-3 N 12114036
Data: I = 10.0 A
L
= 20cm = 0.2m
a = 90° (because force is maximum)
B
= ?
14.2 How fast must a proton move in a magnetic
field 2.50 ´ 10-3 T such
that the magnetic force is equal to its weight?
B = 2.5 ´ 10-3 12114037
Data:
q = e = 1.6 ´ 10-19 C
m
= 1.67 ´
10-27 kg
q = 90°
v
= ?
F = W (given)
14.3 A velocity selector has a
magnetic field of 0.30T. If a perpendicular electric field of 10,000Vm-1
is applied, what will be the speed of the particle that will pass though the
selector? 12114038
B = 0.3T
Data: E = 10,000 vm-1
v =?
14.4 A coil of 0.1m´0.1m and of 200 turns carrying a current of 1.0 m A is
placed in a uniform magnetic field of 0.1 T. Calculate the maximum torque that
acts on the coil?
Ans. B = 0.1 T 12114039
Data: A = 0.1 ´ 0.1
= 0.01m2
N = 200
I = 1.0 mA = 10-3
A
a = 0o
14.5 A power line 10.0m high carries
a current 200A. Find the magnetic field of the wire at the ground. 12114040
Data: I = 200 m
r = 10 m
mo
= 4p´
10-7wb A-1 m-1
B
= ?
14.6 You are asked to design a
solenoid that will give a magnetic field of 0.10 T, yet the current must not
exceed 10.0A. Find the number of turns per unit length that the solenoid should
have? 12114041
B = 0.1 T
Data: I = 10.0 A
mo
= 4p´
10-7Wb A-1 m-1
n = ?
14.7 What current should pass
through a solenoid that is 0.5 m long with 10,000 turns of copper wire so that
it will have a magnetic field of 0.4T? (Board 2013) 12114042
Data: Length =L=0.5m
No.
of turns =10,000
Magnetic
field = B= 0.4T
Current
through solenoid = I = ?
14.8 A galvanometer having an
internal resistance Rg = 15.0 W
gives full-scale deflection with current Ig = 20.0mA. It is to be
converted into an ammeter of range 10.0A. Find the value of shunt resistance Rs? 12114043
Data: Rg = 15 W
Ig =
20mA
= 0.02A
I = 10A
Rs
=?
14.9 The resistance of galvanometer
is 50.0W and reads full-scale deflection with a
current of 2.0mA. Show by a diagram how to convert this galvanometer into a
voltmeter reading 200V full scale. 12114044
Rg = 50 W
Data: Ig = 2.0mA = 0.002A
V = 200 Volts
Rh= ?
14.10 The resistance of
galvanometer coil is 10.0Wand reads full
scale with a current of 1.0 mA. What should be the values of resistance R1,
R2, and R3 to convert this galvanometer into a
multi-range ammeter of 100, 10.0 and 1.0A as shown in the fig?
12114045
Data: Rg = 10 W
Ig =
1.0 mA = 0.001 A
I1 =
100 A
I2 =
10 A
I3 =
1 A
R1=
?
R2=
?
R3=
?
Unit 15
ELECTRO
MAGNETIC INDUCTION
Q.1 What do you mean by induced e.m.f. and induced current? 12115001
Q.2 Narrate different methods used to produce an inducede.m.f. 12115002
Q.3 What is motional e.m.f.? Derive an expression for it. 12115003
Q.4 State and explain Faraday’s law of electromagnetic induction. (B. 2010, 2013) 12115004
Q.5 State and explain Lenz’s law. 12115005
Q.6 Explain that Lenz’s law is also a
statement of Law of conservation of energy.
12115006
Q.7 Explain the term mutual induction. Also give its unit. 12115007
Q.8 Define and explain self induction. 12115008
Q.9 Derive an expression for energy stored in an inductor. Also express
the energy stored in term of magnetic induction. (Board 2013, 14) 12115009
Q.10 Describe the principle, construction and working of A.C
generator. Also find expression
for induced e.m.f. and current. 12115010
Q.11 What is D.C generator? Describe its construction and working. 12115011
Q.12 What is a D.C motor? Describe its construction and working. 12115012
Q.13 What do you mean by back e.m.f. in motors? (Board
2014, 16) 12115013
Q.14 (a) What
is a transformer? Describe its construction, principle and working.12115014
(b) How power is lost in transformer?
SHORT QUESTIONS
15.1 Does the
induced emf in a circuit depend on the resistance of the circuit? Does the
induced current depend on the resistance of the circuit? (Board 2016) 12115015
15.2 A square loop of wire is
moving through a uniform magnetic field. The normal to loop is oriented
parallel to the magnetic field. Is emf induced in the loop? Give a reason for
your answer. 12115016
15.3: A light metallic ring is
released from above into a vertical bar magnet. Viewed for above does the
current flow clock wise or anticlockwise in the ring? 12115017
15.4 What is the direction of
the current through resistance R in fig. as switch ‘S’ is
(a) Closed (b)
Opened 12115018
15.5 Does the induced emf
always act to decrease the magnetic flux through a circuit? (Board 2013, 14, 15) 12115019
15.6 When the switch in the
circuit is closed a current is established in the coil and metal rings jumps
upward. Why?
Describe what would happen to the ring if the battery polarity were
reversed? 12115020
15.7 The Fig. shows a coil of
wire in the xy-plane with a magnetic field directed along the y-axis. Around
which of the three co-ordinate axes should the coil be rotated in order to
generate an emf and a current in the coil? ` 12115021
15.8 How would you position a
flat loop of wire in a changing magnetic field so that there is no emf induced
in the loop?
(Board
2016) 12115022
15.9 In a certain region the
earth’s magnetic field point vertically down. When a plane flies due north,
which wingtip is positively charged?
(Board 2014, 15)12115023
15.10: Show that e and
have the same units. (Board 2013, 15) 12115024
15.11 When an electric
motor, such as an electric drill, is being used, does it also act as a
generator? If so what is the consequence of this? (Board 2015) 12115025
15.12 Can a D.C motor be turned
into a D.C generator? What changes are required to be done? (Board 2015,16) 12115026
15.13 Is it possible to
change both the area of the loop and the magnetic field passing through the
loop and still not have an induced emf in the loop? 12115027
15.14 Can an electric motor be used to drive an
electric generator with the output from the generator being used to operate the
motor? 12115028
15.15 A suspended magnet is oscillating freely in a horizontal plane.
The oscillations are strongly damped when a metal plate is placed under the
magnet. Explain why this occurs?
(Board 2010) 12115029
15.16 Four unmarked wires emerge from a
transformer. What steps would you take to determine the turns ratio?
(Board 2013, 16) 12115030
15.17 (a) Can a step-up transformer increase the power level?
(Board 2015, 16) 12115031
(b) In
a transformer, there is no transfer of charge from the primary to the
secondary. How is, then the power transferred?
15.18 When the primary of
a transformer is connected to a.c. mains the current in it.
12115032
(a) Is very small if the secondary circuit is open, but
(b) Increase when the secondary circuit is closed.
Explain these facts.
Solved Examples
Example 1: 12115033
A metal rod
of length 25cm is moving at a speed of 0.5ms-1 in a direction
perpendicular to a 0.25T magnetic field. Find the emf produced in the rod.
Example 2: 12115034
A
loop of wire is placed in a uniform magnetic field that is perpendicular to the
plane of the loop. The strength of the magnetic field is 0.6T. The area of the
loop begins to shrink at a constant rate of 
. What is the magnitude of emf induced in the loop while it
is shrinking?
Example 3: 12115035
An
emf of 5.6V is induced in a coil while the current in a nearby coil is
decreased from 100A to 20A in 0.02s. What is the mutual inductance of the two
coils? If the secondary has 200 turns, find the change in flux during this
interval.
Example 4: 12115036
The
current in a coil of 1000 turns is changed from 5A to zero in 0.2s. If an
average emf of 50V is induced during this interval, what is the self inductance
of the coil? What is the flux through each turn of the coil when a current of
6A is flowing?
Example 5: 12115037
A
solenoid coil 10.0cm long has 40 turns per cm. When the switch is closed, the
current rises from zero to its maximum value of 5.0 A in 0.01 s. Find the
energy stored in the magnetic field if the area of cross-section of the
solenoid be 28 cm2.
Example 6: 12115038
An
alternating current generator operating at 50 Hz has a coil of 200 turns. The
coil has an area of 120 cm2. What should be the magnetic field in
which the coil rotates in order to produce an emf of maximum value of 240
volts?
Example 7: 12115039
A
permanent magnet D.C motor is run by a battery of 24 volts. The coil of the
motor has a resistance of 2 ohms. It develops a back emf of 22.5 volts when
driving the load at normal speed. What is the current when motor just starts
up? Also find the current when motor is running at normal speed.
Example 8: 12115040
The
turns ratios of a step up transformer is 50. A current of 20 A is passed
through its primary coil at 220 volts. Obtain the value of the voltage and
current in the secondary coil assuming the transformer to be ideal one.
PROBLEMS
15.1 An emf of 0.45V is induced between the ends
of a metal bar moving through a magnetic field of 0.22 T. What field strength
would be needed to produce on emf of 1.5V between the ends of the bar, assuming
that all other factors remain the same? 12115041
Data. e1 = 0.45V
e2
= 1.5 Volt
B1 =
0.22T
B2= ?
15.2 The flux density B in a region between the
pole faces of a horse shoe magnet is 0.5 Wb/m2 directed vertically
downwards. Find the emf induced in a straight wire 5.0cm long, perpendicular to
B when it is moved in a direction at an angle of 60o with the
horizontal with a speed of 100 cm/s. 12115042
Data:
B
= 0.5 Wb/m2
L
= 5.0 cm = 0.05m
v
= 100cm/sec = 1m/s
Angle
with horizontal = f
= 60o
Angle
of v with B =q = 90o-60o = 30o
15.3 A coil of wire has 10
loops. Each loop has an area of 1.5 ´ 10-3 m2. A magnetic
field is perpendicular to the surface of each loop at all times. If the
magnetic field is charged from 0.05T to 0.06T in 0.1s, find the average emf
induced in the coil during this time? 12115043
Data:
N = 10
A
= 1.5 ´
10-3m2
q = 0o
B1 =
0.05T
B2 =
0.06T
rt
= 0.1 sec
e = ?
15.4 A circular coil has 15 turns of radius 2 cm each. The plane of the coil
is inclined at 400 to a uniform magnetic field of 0.2T. If the field
is increased to 0.5T in 0.2 sec, find the magnitude of the induced emf. 12115044
Data:
L = 2cm = 0.02 m
N = 15
q = 90o – 40o
= 50o (from fig)
B1 = 0.2T
B2 = 0.5T
rt
= 0.2
e = ?
15.5 Two coils are placed side by side. An emf of
0.8 V is observed in one coil when the current is changing at the rate of 200 As-1
in the other coil. What is the mutual inductance of the coils?
(Board 2015)12115045
Data:
Vs =
0.8 Volt
=200As-1
M = ?
15.6 A pair of adjacent coils has a mutual
inductance of 0.1H. If the current in the primary changes from 0 to 10A in
0.25s, what is the average induced emf in the secondary? What is the change in
flux in it if the secondary has 500 turns?
12115046
Data: M = 0.75 H
I1
= 0
I2
= 10A
rt
= 0.025 sec
Change in flux = rФs
= ?
15.7 A solenoid has 250 turns and its self-inductance
is 2.4 mH. What is the flux through each turn when the current is 2A? What is
the induced emf when the current changes at 20As-1? 12115047
Data: N = 250
L
= 2.4mH = 2.4 ´
10-3H
I = 2A
=
20 As-1
= ?
eL=
?
15.8 A solenoid of length 8.0
cm and cross sectional area 0.5 cm2 has 520 turns.
Find the self-inductance of the solenoid when the core is air. If the current
in the solenoid increases through 1.5A in 0.2 sec, find the magnitude of
induced emf in it.
12115048
Data: 
= 8cm = 0.08m
N = 520 turns
A = 0.5cm2
= 0.5 ´
10-4m2
rI =
1.5A
rt
= 0.2 sec
eL=
?
15.9 When current through a coil changes from
100 mA to 200 mA in 0.005s, an induced emf of 40 mV is produced in the coil. 12115049
(a) What is the self-inductance of the coil?
(b) Find
the increase in the energy stored in the coil.
Data:
I1
= 100mA = 0.1A
I2
= 200mA = 0.2A
rt
= 0.005 sec
e =
40mV = 40 ´ 10-3V
L = ?
rU
= ?
15.10 Like any field, the Earth’s magnetic field
stores energy. Find the magnetic energy stored in a space where strength of
earth’s field is 7´10-5
T, if the space occupies an area of 10 ´ 108
m2 and has a height of 750 m. 12115050
Data.
h = 750m
B = 7 ´ 10-5T
A = 10 ´ 108m2 =
109m2
mo
= 4p´
10-7Wb A-1m-1
U = ?
15.11 A square coil of side 16
cm has 200 turns and rotates in uniform magnetic field of magnitude 0.05 T. If the
peak emf is 12V, what is the angular velocity of the coil?
Data: (Board 2014, 15)12115051
A = 16 ´ 16 =
256 cm2
A= 256 ´ 10-4
m2
B = 0.05T
eo
= 12V
N = 200
w= ?
15.12 A
generator has a rectangular coil consisting of 360 turns. The coil rotates at
420 rev per min in 0.14 T magnetic field. The peak value of emf produced by the
generator is 50 V. If the coil is 5.0 cm wide, find the length of the side of
the coil.
12115052
Data.
B = 0.14T
eo
= 50 volt
b = 5.0 cm = 0.05m
w= 420
rev.min-1
Where
1 rev = 2p rad
w =
w = 47
rad /sec
N=360
= ?
15.13 It is desired to make an A.C. generator that can produce an emf of
5 kV with 50 Hz frequency. A coil of area 1 m2 consisting of 200
turns is used as armature. What should be the magnitude of the magnetic field
in which the coil rotates? 12115053
Data:
eo = 5kV
=
5000V
f =
50Hz
A = 1m2
N =
200
B = ?
15.14 The back emf in a motor is 120 V when the
motor is turning at 1680 rev per min. What is the back emf when the motor turns
3360 rev per min? 12115054
Data.
e1
= 120 V
w1
= 1680 rev/min
w2
= 3360 rev/min
e2
= ?
15.15 A D.C motor operates at 240 V and has a
resistance of 0.5 W.
When the motor is running at normal speed, the armature current is 15 A. Find
the back emf in the armature. 12115055
Data.
V = 240V
R = 0.5 W
I = 15A
e = ?
15.16 A copper ring has radius
of 4.0 cm and resistance of 1.0 m W. A
magnetic field is applied over the ring, perpendicular to its plane. If the
magnetic field increases from 0.2 T to 0.4 T in a time interval of 5 ´ 10-3 s, What is the current in the ring
during? 12115056
Data.
r =
4.0 cm= 0.04m
R =
1.0mW = 10-3W
B1
= 0.2T
B2
= 0.4T
rt
= 5 ´ 10-3sec
I = ?
15.17 A coil of 10 turns and
35cm2area is a perpendicular magnetic field of 0.5 T. The coil is
pulled out of the field in 1.0s. Find the induced emf in the coil as it is
pulled out of the field. 12115057
Data:
A = 35 cm2=
35 ´
10-4 m2
B1 =
0.5T
B2 =
1.0T
rt
= 1.0S
N = 10
e = ?
15.18 An ideal step down transformer is connected to main supply of 240
V. It is desired to operate a 12 V, 30 W lamp. Find the current in the primary
and the transformation ratio.(Board 2010) 12115058
Data:
P =
30W
VP =
240V
VS =
12V
IP =
?
= ?
UNIT 16
ALTERNATING CURRENT
Q.1 What is alternating current? Prove that output voltage of an A.C.
generator varies sinusoidally with time. 12116001
Q.2 Define the following terms: 12116002
(i) Instantaneous
value
(ii) Peak
value
(iii) Peak
to Peak value
1. Q.3 What is meant by root
mean square value of current and voltage and establish relations between r.m.s
value and Peak value of alternating voltage and current. 12116003
Q.4 Describe the following: 12116004
(i)
Phase of A.C
(ii)
Phase lag and phase lead
(iii)
Vector representation of alternating
quantity.
i.
Q.5 What do you mean by A.C. circuit?
Describe A.C. through A resistor. 12116005
Q.6 Describe A.C. though capacitor. 12116006
Q.7 What is inductor? Describe passage of A.C.
through an inductor. 12116007
Q.8 What do you mean by term impedance? 12116008
Q.9 What is R-C
circuit? Find impedance and phase difference between voltage and current. (Board 2013, 16) 12116009
Q.10 What is R-L series circuit?
Find impedance of R-L and phase difference between voltage and current. (Board 2013) 12116010
Q.11 Describe power loss in an A.C. circuit. 12116011
Q.12 Explain RLC
series circuit or series resonance circuit in detail. Also point out resonance
and important characteristics. (Board 2015)12116012
Q.13 Explain RLC
parallel circuit or parallel resonance circuit. Also point out important
properties of the current. 12116013
Q.14 Discuss
three phase A.C. supply? What are its advantages? 12116014
Q.15 Describe the principle of metal detectors. 12116015
Q.16 What
is a choke? What is its use? (Board 2013, 16) 12116016
Q.17 What
are electromagnetic waves? 12116017
Q.18 Describe principle of generation,
transmission, and reception of electromagnetic waves. 12116018
Q.19 What do you know about modulation? 12116019
SHORT
QUESTIONS
16.1 A
sinusoidal current has rms value of 10 A. What is the maximum or peak value? (Board
2014, 16) 12116020
or Io = 14.14A 12116021
16.2 Name
the device that will (a) permit flow of direct current but oppose the flow of
alternating current (b) permit flow of alternating current but not the direct
current. (Board
2013, 14) 12116022
16.3 How
many times per second will an incandescent lamp reach maximum brilliance when
connected to a 50 Hz source? (Board2010, 2013, 16) 12116023
16.4 A
circuit contains an iron-cored inductor, a switch and a D.C. source arranged in
series. The switch is closed and after an interval re-opened. Explain why a
spark jumps across the switch contacts? (Board 2015) 12116024
16.5 How
does doubling the frequency affect the reactance of (a) an inductor (b) a
capacitor? (Board
2013, 14, 15, 16) 12116025
16.6 In
a R-L circuit, will the current lag or lead the voltage? Illustrate your answer
by a vector diagram. 12116026
16.7
A choke coil placed in series with an electric lamp in an A.C. circuit causes
the lamp to become dim. Why is it so? A
variable capacitor added in series in this circuit may be adjusted until the
lamp glows with normal brilliance. Explain, how this is possible. 12116027
16.8 Explain
the conditions under which electromagnetic waves are produced from a source. (Board 2015) 12116028
16.9 How
the reception of a particular radio station is selected on your radio set?
(Board
2016) 12116029
16.10 What
is meant by A.M. and F.M.?
(Board
2013, 15, 16) 12116030
Solved Examples
Example 1: 12116031
An A.C.
voltmeter reads 250 V. What is its peak and instantaneous values if the
frequency of alternating voltage is 50 Hz?
Example 2: 12116032
A 100 mF
capacitor is connected to an alternating voltage of 24V and frequency 50 Hz.
Calculate (Board 2015)
(a) The
reactance of the capacitor, and
(b) The
current in the circuit
Example 3: 12116033
When 10 V are
applied to an A.C. circuit, the current flowing in it is 100 mA. Find its
impedance.
Example 4: 12116034
At what
frequency will an inductor of 1.0 H have a reactance of 500 W?
Example 5: 12116035
An iron core coil of 2.0 H and
50 W
is placed in series with a resistance of 450 W. An A.C. supply of 100 V,
50 Hz is connected across the circuit. Find (i) the current flowing in the
coil, (ii) phase angle between the current and voltage.
Example 6: 12116036
A circuit consists of a
capacitor of 2 mF and a resistance of 1000 W
connected in series. An alternating voltage of 12 V and frequency 50 Hz is
applied. Find (i) the current in the circuit, and (ii) the average power
supplied.
Example 7: 12116037
Find the capacitance required
to construct a resonance circuit of frequency 1000 kHz with an inductor of 5
mH. (Board 2014, 16)
PROBLEMS
16.1 An
alternating current is represented by the equation I = 20 sin 100 pt. Compute its frequency
and the maximum and rms values of current.
Data: I
= Io sin100pt 12116038
f = ?
Io = ?
Irms=
?
16.2 A
sinusoidal A.C. has a maximum value of 15 A. What are its rms values? If the
time is recorded from the instant the current is zero and is becoming positive,
what is the instantaneous value of the current after s, given the frequency is 50 Hz. 12116039
Data:
Io = 15A,
t = sec,
f = 50Hz
Irms= ?,
I = ?
16.3 Find
the value of the current and inductive reactance when A.C. voltage of 220 V at
50 Hz is passed through an inductor of 10 H. 12116040
Data: V
= 220v
L = 10H
f
= 50Hz
Irms= ?
XL =?
16.4 A
circuit has an inductance of H and resistance of 2000 W. A
50 Hz A.C. is supplied to it. Calculate the reactance and impedance offered by
the circuit. 12116041
Data:
R = 2000W
L = H
f = 50Hz
Z = ?
XL= ?
16.5 An
inductor of pure inductance H is connected in series with a resistance of 40W. Find (i) the peak value of the current (ii) the rms
value, and (iii) the phase difference between the current and the applied
voltage V = 350 sin(100 pt). 12116042
Data: L
= H
R = 40W,
V = 350 sin (100pt)
Io= ?
Irms= ?
q=
?
16.6 A
10 mH, 20 W coil is connected across
240 V and Hz source. How much power does it dissipate? 12116043
Data:
L = 10 mH = 10 ´
10-3 = 0.01 H
R = 20 W
V = 240V
f = Hz
P = ?
16.7 Find
the value of the current flowing through a capacitance 0.5mF when connected to a source of 150V at 50 Hz.
12116044
Data:
Vrms = 150V
C = 0.5mF = 0.5 ´10-6 F
C = 5 ´ 10-7F
f = 50HZ
Irms=?
16.8 An
alternating source emf 12 V and frequency 50 Hz is applied to a capacitor of
capacitance 3mF in series with a
resistor of resistance 1kW.
Calculate the phase angle. 12116045
Data:
R
= 1kW
= 1000W
C = 3 ´
10-6 F
V = 12V
f = 50Hz
q
= ?
16.9 What
is the resonant frequency of a circuit which includes a coil of inductance 2.5
H and a capacitance 40mF?
(Board 2013) 12116046
Data:
L
= 2.5H
C = 40mF
fr= ?
16.10 An
inductor of inductance 150mF is
connected in parallel with a variable capacitor whose capacitance can be
changed from 500 pF to 20 pF. Calculate the maximum frequency and minimum
frequency for which the circuit can be tuned. 12116047
Data:
L
= 150mH
L = 150 ´ 10-6H
Cmax = 500pf = 500 ´ 10-12F
Cmin = 20pf = 20 ´ 10-12F
fmax =?,
fmin = ?
UNIT 17
PHYSICS OF SOLIDS
Q.1 How would you
classify solids? 12117001
Q.2 Define
and explain the mechanical property of solids and deformation of material.12117002
Q.3 Define stress and strain. What are their
SI units? Differentiate between tensile, compressive and shear modes of stress
and strain. (Board 2013, 14) 12117003
Q.4 What is meant by
strain energy? How can it be determined from the force-extension graph? 12117004
Q.5 Distinguish
solids into conductor, insulator and semi-conductor on the basis of electrical behavior. 12117005
Q.6 Describe the
formation of energy bands in solids. Explain the difference amongst electrical behavior
of conductors, insulators and semi-conductor in terms of energy band theory. 12117006
Q.7 Distinguish between intrinsic and
extrinsic semiconductors. How would you obtain
n-type and p-type material from pure silicon? Illustrate it by schematic
diagram.
Ans: Intrinsic and Extrinsic Semiconductors: (Board 2010, 15, 16) 12117007
Q.8 Discuss the
mechanism of electrical conduction by holes and electrons in a pure
semiconductor element. (Board 2013) 12117008
Q.9 Write a note super conductor. (Board
2013)12117009
Q.10 What is meant
by magnetic properties of solids? Explain para, dia and ferromagnetic
substances. Give examples of each. (Board 2013) 12117010
Q.11 What is mean by hysteresis loop? How is it used in the
construction of a transformer?
Hysteresis Loop: 12117011
SHORT QUESTIONS
17.1 Distinguish between crystalline,
amorphous and polymeric solids.
(Board 2015,16) 12117012
17.2 Define stress and strain. What are their
SI units? Differentiate between tensile, compressive and shear modes of stress
and strain. (Board 2014) 12117013
17.3 Define modulus of elasticity. Show that
the units of modulus of elasticity and stress are same. Also discuss its three
kinds. (Board 2014,
16)12117014
17.4 Draw a stress-strain curve for a ductile
material and then define terms: Elastic limit, Yield point and ultimate tensile
stress. 12117015
17.5 What is meant by strain energy? How can
it be determined from force-extension graph? (Board 2016) 12117016
17.6 Describe the formation of energy bands in
solids. Explain difference amongst electrical behavior of conductors,
insulators and semiconductors in terms of energy band theory. (Board 2014)12117017
17.7 Distinguish between intrinsic and extrinsic
semi conductors. How would you obtain n-type and p-type material from pure
silicon? Illustrate it by schematic diagram. (Board 2016) 12117018
17.8 Discuss the mechanism of electrical
conduction by holes and electrons in a pure semiconductor element. 12117019
17.9 Write a note on super conductors.
12117020
17.10 What is meant by Para, Dia and Ferromagnetic
substances? Give examples for each. (Board 2014) 12117021
17.11 What is
meant by Hysteresis loss? How is it used in construction of a transformer? (Board 2015,16)
12117022
Solved Examples
Example 1: 12117023
A steel wire 12 mm in diameter
is fastened to a log and is then pulled by tractor. The length of steel wire
between the log and the tractor is 11 m. A force of 10,000 N is required to
pull the log. Calculate (a) the stress in the wire and (b) the strain in the
wire. (c) How much does the wire stretch when the log is pulled? (E = 200 ´ 109 Nm-2)
Data: D
= 12mm = 12 × 10-3m
R
= = 6 × 10-3m
= 11m
F
= 10,000 N
Y
= 200 × 109 Nm-2
Stress
= s=
?
Strain
= e=
?
∆
= ?
PROBLEMS
17.1 A 1.25 cm diameter
cylinder is subjected to a load of 2500 kg. Calculate the stress on the bar in
mega pascals?
(Board 2013) 12117024
Data:
d
= 1.25 cm = = 0.0125 m
g = 9.8 ms-2
m = 2500 kg
Stress = s= ?
17.2 A 1.0 m long copper
wire is subjected to stretching force and its length increases by 20 cm.
Calculate the tensile strain and the percent elongation which the wire
undergoes. (Board 2015,16) 12117025
Data:
= 1.0 m
D
= 20 cm = 0.2 m
Strain = E= ?
% elongation = ?
17.3 A wire 2.5 m long and
cross section area 10-5 m2 is stretched 1.5 mm by a force
of 100 N in the elastic region. Calculate
(Board 2014) 12117026
(i) Strain
(ii) Young’s Modulus.
(iii) The energy stored in wire = U = ?
Data:
= 2.5 m
A
= 10-5 m2
D
= 1.5 mm
F
= 100 N.
17.4 What stress would
cause a wire to increase in length by 0.01% if the Young’s modulus of the wire
is 12 ´ 1010 Pa. What force would produce this
stress if the diameter of wire is 0.56 mm?
12117027
Data: e= = 0.01 ´= 10-4
Y = 12 ´ 1010 Pa
d = 0.56 mm = 0.56 ´ 10-3
m
Stress = s= ?
Force = F = ?
17.5 The length of a steel
wire is 1.0 m and its cross-sectional area is 0.03x10-4 m2.
Calculate the work done in stretching the wire when force of 100 N is applied
with in the elastic region. Young’s modulus of steel is 3.0 x 1011
Nm-2. 12117028
Data:
= 1.0 m
A = 0.03 ´ 10-4 m2
F = 100 N.
Y = 3.0 ´ 1011 Nm-3
W = ?
17.6 A cylindrical copper
wire and a cylindrical steel wire each of length 1.5m and diameter 2.0 mm are
joined one end to form a composite wire 3.0 m long. The wire is loaded until
its length becomes 3.003 m. Calculate the strain in copper
and steel wires and the force applied to
the wire. (Young’s Modulus of Copper is
1.2 ´ 1011 Pa and for steel is 2.0 ´ 1011 Pa).
12117029
Data:
Length of copper wire = 
= 1.5 m
Length of steel wire = = 1.5 m
Total Length = L = + = 1.5 + 1.5 = 3 m
d = 2.0 mm
d = 2 ´
10-3 m
r = 1 ´
10-3 m
A = pr2
= 3.14 ´ 10-6
m2
= 3.003 m
D = - = 3.003 - 3 = 0.003
Young’s Modulus of copper wire
= Yc = 1.2 ´ 1011 Pa
Young’s Modulus of steel wire
= Ys = 2.0 ´ 1011
Pa
Strain in copper wire
=ec
= ?
Strain in steel wire = es= ?
Force = F = ?
UNIT 18
ELECTRONICS
Q.1 What is P-N junction? What is “depletion region”? 12118001
Q.2 What is meant by biasing? Discuss its different types. 12118002
Q.3 What is meant by rectification? Discuss half wave and full wave
rectification (or
rectifiers). (Board 2014) 12118003
Q.4 What are specially designed P-N junction? Discuss. Also give their
uses. 12118004
Q.5 What is transistor? Discuss its different types, different parts and
operations.
Ans: Transistors: (Board2010,
2013) 12118005
Q.6 How does current flow in a transistor? Also give current gain of a
transistor. 12118006
Q.7 How does transistor work as an amplifier? Explain.
Ans: Transistor As An
Amplifier: (Board 2010,
14) 12118007
Q.8 How does transistor work as a switch? 12118008
Q.9 What is an operational amplifier?
Discuss its different parts and characteristics.
OPERATIONAL AMPLIFIER: (Board 2015) 12118009
Q.10 How does operational amplifier work as
inverting amplifier? Also find output gain?
Ans: Op-Amp as Inverting Amplifier: (Board 2016) 12118010
Q.11 How does operational amplifier work as
non-inverting amplifier? Also find output gain. (Board 2015)
12118011
Q.12 How does operational amplifier is used as comparator? 12118012
And narrate
how can comparator be used to design night switch.
Q.13 What is meant by digital system? Also discuss Boolean algebra. 12118013
Q.14 What are fundamental logic gates?
Explain. 12118014
Q.15 What are logic gates other than fundamental logic gates? 12118015
Q.16 How gates are applied to monitor physical parameters? Explain. 12118016
SHORT QUETIONS
18.1
How
does the motion of an electron in an n-type substance differ from the motion of
holes in p-type substance?
(Board 2013, 2016) 12118017
18.2
What
is the net charge on a n-type and p-type substances? (Board 2014) 12118018
18.3
The
anode of a diode is 0.2V positive with respect to its cathode. Is it forward
biased? 12118019
18.4
Why charge carriers are not present in the
depletion region? (Board . 2013) 12118020
18.5
What
is effect of forward and reverse biasing of a diode on the width of depletion
region? (Board 2015) 12118021
18.6
Why
ordinary silicon diode do not emit light? (Board 2014,16) 12118022
18.7
Why a
photodiode is operated in reverse state? (Board 2015,16) 12118023
18.8
Why
is base current in a transistor very small? (Board
2013, 15,16) 12118024
18.9
What
is biasing requirements of the junction of a transistor for its normal
operation? Explain how these are met in common emitter amplifier?
(Board 2013) 12118025
18.10
What
is principle of virtual ground? Apply it to find the gain of an inverting
amplifier. 12118026
18.11 The inputs of a gate are 1 and 0. Identify the gate if its output is
(a) 0 (b) 1.
12118027
18.12: Tick the correct answer.
i. A diode characteristic curve is a plot
between: 12118028
a. current and time
b. voltage and time.
c. voltage and current
d. forward and reverse voltages.
ii. The colour of light emitted by a LED depends
on 12118029
a.
Its forward bias
b. It’s reverse bias.
c. The amount of forward current
d. the type of
semi-conductor material used.
iii. In a half-wave rectifier the diode conducts
during: 12118030
a. Both halves of the input cycle
b. a portion of the positive half of the input cycle
c. a portion of the negative half of the input cycle
d. one half of the input cycle.
|
iv. In a bridge rectifier of fig. Q. 18.1 when Vi is
positive at point B with respect to point A which diodes are ON. a. D2
and D4 b. D1 and D3 c. D2 and D3 d. D1 and D4. |
12118031
|
v. The common emitter current amplification factor b is
given by12118032
a. b.
c. d.
vi. Truth table of logic function 12118033
a. summarizes its output values.
b. tabulates all its input conditions only
c. display all its input/output
possibilities
d. is not based on logic algebra
vii. The output of a two inputs OR gate is 0 only when its 12118034
a. both inputs are 0
b. either input is 1
c. both inputs are 1
d. either input is 0
viii. A two inputs NAND gate
with inputs A and B has an output 0 if 12118035
a. A is 0
b. B is 0
c. both A and B are zero
d. both A and B are 1
ix. The truth table shown below is for gate. 12118036
a. XNOR
b. OR
c. AND
d. NAND
|
A |
B |
X |
|
0 |
0 |
1 |
|
0 |
1 |
0 |
|
1 |
0 |
0 |
|
1 |
1 |
1 |
Solved Examples
Example 1: 12118037
In a certain circuit, the transistor has a collector current of 10 mA
and a base current of 40 mA. What is the current gain of the transistor?
Example 2: 12118038
Find the
gain of the circuit as shown in Fig. 18.30.
PROBLEMS
18.1 The
current flowing into the base of a transistor is 100 m A. Find its collector current IC, its emitter current IE
and the ratio , if the
value of current gain b is 100.
(Board 2013, 16) 12118039
Data:
IB = 100 mA = 100 ´
10-6A = 10-4A
b =
100
IC
= ?
IE
= ?
= ?
18.2: Figure shows a transistor which operates a
relay as the switch S is closed. The relay is energized by a current of 10 mA.
Calculate the value RB which will just make the relay operate. The
current gain b of the transistor is 200.
When the transistor conducts, its VBE can be assumed to be
0.6V. 12118040
Data:
IC = 10mA = 10 ´ 10-3A
b =
200
VBE = 0.6 V
VCC
= 9 V
RB=
?
18.3 In circuit shown in Fig., there is
negligible potential drop between B and E, where is β is 100, calculate: 12118041
(i) base current
(ii) collector current
(iii) potential drop across RC
(iv) VCE
Data:
VCC = 9 Volt
RC = 1 k W = 1 ´ 1000
W
RB = 800 k W =
800 ´
1000 W
b = 100
VBE = 0
IB = ?
IC = ?
VC= ?
VCE= ?
18.4 Calculate the output of the op-amp circuit
shown in Fig. 12118042
Data: R1 = 10 kW = 10
´
103W
R2= 4 kW = 4 ´ 103W
R3 = 20 kW = 20
´
103 W
Output voltage = V0 = ?
18.5 Calculate the gain of non-inverting
amplifier shown in fig. (Board 2014)12118043
Data:
R = 10 k W = 10 ´ 103W
R2 = 40 k W = 40
´
103W
G = ?
|
Unit |
DAWN
OF MODERN PHYSICS |
|
19 |
Q.1 What is relative motion?
Explain. 12119001
Q.2 What is meant by frame of reference?
Differentiate inertial and non-inertial frame
of reference? (Board 2010) 12119002
Q.3 What is special theory of relativity? Write down its
postulates. Also summarize the results of special theory of relativity. 12119003
Ans: Special Theory of Relativity: (Board
2014)
Q.4 What do you mean by NAVSTAR Navigation System. 12119004
Q.5 What
is black body radiation? Explain intensity distribution diagram. (Board 2014)
Ans: BLACK BODY RADIATION: 12119005
Q.6 How does Planck’s explained
black body radiation? Explain. 12119006
Q.7 Define
photoelectric effect. Describe an experimental arrangement to produce
photoelectrons and state the experimental results. 12119007
Q.8 Explain photoelectric effect on the basic of
Einstein’s quantum theory. Also derive Einstein’s equation. 12119008
Q.9 What is photocell? Write down
its different uses. 12119009
10. What is Compton effect? Calculate Compton wave
shift too. Prove that it explains particle nature of light. 12119010
Q.11 What is pair production?
How does its occur? Explain. 12119011
Q.12 What do you mean by annihilation of matter?
Explain. 12119012
Q.13 Explain wave nature of a particle. 12119013
Q.14 How Davisson and Germer proved wave nature
of a particle experimentally? 12119014
Ans: Davisson and Germer Experiment: (Board 2016)
Q.15 Write note on the wave particle duality. (Board 2016) 12119015
Q.16 What
is electron microscope? Explain it. 12119016
Q.17 Write
a comprehensive note on uncertainty principle. (Board
2013) 12119017
SHORT QUESTIONS
19.1 What are the measurements
on which two observers in relative motion will always agree upon? 12119018
19.2 Does the dilation means that
time really passes more slowly in moving system or that is only seems to pass
more slowly? (Board 2014,
16) 12119019
19.3 If you are moving in a
spaceship at a very high speed relative to earth, would you notice a difference
(a), in your pulse rate (b) in pulse rate of people on Earth?
12119020
19.4 If the speed of light
were infinite, what would the equations of special theory of relativity reduce
to?
(Board 2015,
16) 12119021
19.5 Since mass is a form of
energy, can we conclude that a compressed spring has more mass than the same
spring when it is not compressed? 12119022
19.6 As a solid is heated and begins to glow,
why does it first appear red?
(Board 2013) 12119023
19.7
What happens to total radiation from a black body if its absolutetemperature is
doubled? 12119024
19.8 A beam of red light and a beam of blue
light have exactly the same energy. Which beam contains the greater number of
photons? (Board
2010) 12119025
19.9 Which photon, red, green,
or blue carries the most (a) energy and momentum? (Board 2013, 15) 12119026
19.10 Which has the lower energy
quanta? Radio waves or x-rays.(Board 2015)
12119027
19.11 Does the brightness of a beam of light
primarily depend on the frequency of photons or on the number of photon?
12119028
19.12 When ultraviolet light falls on certain dyes,
visible light is emitted. Why does this not happen when infra-red light falls
on these dyes? 12119029
19.13 Will bright light eject more electrons from a
metal surface than dimmer light of the same colour? 12119030
19.14 Will
smaller frequency light eject greater number of electrons than low frequency
light? 12119031
19.15 When light shines on a surface, is momentum
transferred to the metal surface? 12119032
19.16 Why can red light be used in a photographic
dark room when developing films, blue or white light cannot? 12119033
19.17 Photon A has twice the energy of photon B.
what is the ratio of the momentum of A to that of B?
(Board
2013, 14)
12119034
19.18 Why don’t we observe a Compton effect with
visible light?
(Board 2015, 16) 12119035
19.19 Can pair production take place in vacuum?
Explain. (Board 2014, 16) 12119036
19.20 Is it possible to create a single electron
from energy? Explain.
(Board
2013, 16) 12119037
19.21 If electrons behave only like particles, what
pattern would you expect on the screen after the electrons passes through the
double slit? 12119038
19.22 If an electron and a proton have the same de
Broglie wavelength, which particle has greater speed?
(Board 2015) 12119039
19.23 We do not notice the de Broglie wavelength
for a pitched cricket ball. Explainwhy? 12119040
19.24 If the following particles all have the same
energy, which has the shortest wavelength? Electron, alpha particle, neutron,
proton. 12119041
19.25 When does light behave as a wave? When does
it behave as a particle? 12119042
19.26 What
advantages an electron microscope has over an optical microscope?
(Board 2010, 14)12119043
19.27 If measurements show a precise position for
an electron, can those measurements show precise momentum also? Explain. 12119044
SOLVED EXAMPLES
Example 1: 12119045
The period of a pendulum is
measured to be 3.0 s in the inertial reference frame of the pendulum. What is
its period measured by an observer moving at a speed of 0.95 c with respect to
the pendulum?
Example 2: 12119046
A bar 1.0 m in length and
located along x-axis moves with a speed of 0.75 c with respect to a stationary
observer. What is the length of the bar as measured by the stationary observer?
Example 3: 12119047
Find the mass m of a moving
object with speed 0.8 c.
Example 4: 12119048
Assuming you radiate as does a blackbody at
your body temperature about 37oC, at what wavelength do you emit the
most energy?
Example 5: 12119049
What is the energy of a photon in a beam of
infrared radiation of wavelength 1240 nm?
Example 6: 12119050
A sodium suface is illuminated with light
of wavelength 300 nm. The work function of sodium metal is 2.46 eV.
(a) Find the maximum K.E. of the ejected
electron.
(b) Determine the cut off wavelength for
sodium.
Example
7: 12119051
A 50 keV photon is Compton scattered by a
quasi-free electron. If the scattered photon comes off at 45o, what
is its wave length?
Example
8: (Board 2016) 12119052
A particle of mass 5.0 mg moves with speed
of 8.0 ms-1. Calculate its de Broglie wavelength.
Example
9: 12119053
An electron is accelerated through a Potential
Difference of 50 V. Calculate its de Broglie wavelength.
Example 10: 12119054
The life time of an electron in an excited
state is about 10-8 s. What is its uncertainty in energy during this
time?
Example 11:
An electron is to be confined to a box of
the size of the nucleus (1.0 ´ 10-14 m). What would the speed
of the electron be if it were so
confined? (Board 2015) 12119055
PROBLEMS
Q.1 A particle called the pion
lives on the average only about 2.6 ´ 10-8
s when at rest in the laboratory. It then changes to another form. How long
would such a particle live when shooting through the space at 0.95? 12119056
Data: v = 0.95
c
to = 2.6
´ 10-8 s
t = ?
Q.2 What is the mass of a 70 kg man
in a space rocket traveling at 0.8 c from us as measured from Earth? 12119057
Data: mo = 75
kg
v = 0.8c
m = ?
Q.3 Find the energy of photon
in: 12119058
(a) Radio wave of wavelength 100
m
(b) Green light of wavelength 550
nm
(c) X-ray with wavelength 0.2 nm
Data:
Wavelength of radio wave = 
= 100 m
Wavelength of green light =
= 550 nm
=
550 ´
10-9 m
Wavelength of X-ray = 
= 0.2 nm
=
0.2 ´
10-9 m
(a) Energy in photon in radio wave=E1= ?
(b) Energy in photon in green light=E2=?
(c) Energy in photon in X-ray = E3= ?
Q.4 Yellow light of 577 nm
wavelength is incident on a cesium surface. The stopping voltage is found to be
0.25 V. Find 12119059
(a) The maximum K.E. of the photo-electrons.
(b) The work function of cesium
Data:
=577 nm
= 577 ´ 109
m
Vo=0.25
V
h=6.63
´
10-34 J.s
(a) Max. K.E. of photo electron =
(K.E)max = ?
(b) Work function = f= ?
Solution:
Q.5 X-rays of wavelength 22 pm are
scattered from carbon target. The scattered radiation are being viewed at 85o
to the incident beam. What is Compton shift? 12119060
Data: 
=22 pm= 22 ´ 10-12
m
q=85o
Compton shift =
D=?
Q.6 A 90 keV X-ray photon is fired
at a carbon target and Compton scattering occurs. Find the wavelength of the
incident photon and the wavelength of the scattered photon for scattering angle
of (a) 30o (b) 60o. 12119061
Data: E=90 keV= 90 ´ 103eV
=90
´
103´
1.6 ´
10-19 J
=144
´
10-16 J
(a)
Wavelength of incident photon = 
= ?
(b)
Wavelength of scattered photon
= 
= ? (at
=30o)
(c)
Wavelength of scattered photon
= 
= ? (at
=60o)
Q.7 What is the maximum wavelength
of the two photons produced when a positron annihilates an electron? The rest
mass energy of each is 0.51 MeV. 12119062
Data:
Rest
Mass energy of each photon
=E = 0.51 MeV
=
0.51 ´106eV
=
0.51 ´
106 x 1.6 ´ 10-19 J
E
= 8.16 ´
10-14 J
= ? (For each photon)
Q.8 Calculate the wavelength of:12119063
(a) a 140 ball moving at 40 ms-1
(b) a proton moving at the same
speed
(c) an electron moving at the
same speed
Data:
M=
140 g=0.14 kg
v=40
m/s
=?
Mass
of electron=9.1´10-31kg
Mass
of proton= 1.67´10-27kg
Q.9 What is de Broglie wavelength
of an electron whose kinetic energy is 120 eV? (Board 2014) 12119064
Data:
K.E. = 120 eV
=
120 ´
1.6 ´
10-19 J
K.E
=192 ´
10-19J
Mass
of electron m = 9.1´10-31kg
=?
Q.10 An electron is placed in a box about the size of an atom that is
about 1.0´10-10m. What is
the velocity of the electrons?
Data: 12119065
Size of box L = 1.0 ´ 10-10m
m=9.1
´
10-31kg
h=
6.62 ´
10-34 J s
Velocity of electrons v = ?
|
Unit |
ATOMIC
SPECTRA |
|
20 |
Q.1 What is
spectroscopy? Write the names of its types. (Board 2013) 12120001
Q.2 What is atomic spectrum? How can it be
obtained? Discuss different series in the visible region of electromagnetic
spectrum. 12120002
Q.3 State basic
postulates of Bohr’s atomic model. How did de-Broglie deduce Bohr’s 2nd
postulate? (Board 2013, 15, 16) 12120003
Q.4 Derive
expression for radii of quantized orbit. (Board 2013, 16) 12120004
Q.5 Derive an expression for the quantized energy of the orbit. 12120005
Q.6 Derive an
expression for hydrogen spectrum, using 3rd postulate of Bohr’s
theory.
OR 12120006
Explain
hydrogen emission spectrum.
Q.7 How does the inner shell transitions of
electron produce characteristics X-rays?
(Board 2015) 12120007
Q.8 What is
continuous X-rays spectrum? How is it produced? 12120008
Q.9 Write down
properties and uses of X-rays. 12120009
Q.10 What is CAT Scanner? (Board 2016) 12120010
Q.11 What is
uncertainty within the atom regarding position of electrons? 12120011
Q.12 What is
laser? Explain its working. (Board 2014) 12120012
Q.13 What is helium-neon laser? Explain. 12120013
Q14. Describe different uses of laser in medicine and industry. 12120014
a.
SHORT
QUESTIONS
20.1
Bohr’s
theory of hydrogen atom is based upon several assumptions. Do any of these
assumptions contradict classical physics? 12120015
20.2
What
is meant by a line spectrum? Explain, how line spectrum can be used for the
identification of elements?
(Board 2014, 16) 12120016
20.3
Can
the electron in the ground state of hydrogen absorb a photon of energy 13.6 eV
and greater than 13.6 eV?
(Board 2014) 12120017
20.4
How
can the spectrum of hydrogen contain so many lines when hydrogen contains one
electron? 12120018
20.5
Is
energy conserved when an atoms emits photon of light?(Board 2013, 15)12120019
20.6
Explain
why a glowing gas gives only certain wavelengths of light and why that gas is
capable of absorbing the same wavelengths? Give a reason why it is transparent
to other wavelengths? 12120020
20.7
What
do you mean when we say that the atom is excited?(Board 2013)12120021
20.8
Can
X-rays be reflected, refracted diffracted and polarized just like any other
waves? Explain. (Board 2014) 12120022
20.9
What
are the advantages of lasers over ordinary light? (Board
2013, 16) 12120023
20.10
Explain
why laser action could not occur without population inversion between atomic
levels?
(Board
2014, 15, 16) 12120024
Solved Examples
Example 1: 12120025
Find the
speed of the electron in the first Bohr orbit. (Board 2015)
PROBLEMS
20.1 A hydrogen atom is in its
ground state (n = 1). Using Bohr’s theory, calculate (a) the radius of the
orbit, (b) the linear momentum of the electron, (c) the angular momentum of the
electron, (d) the kinetic energy, (e) the potential energy, and (f) the total
energy. 12120026
Data: n = 1
e
= 1.6 ´
10-19C
h = 6.63 ´ 10-34Js
k
=
= 9 ´ 109
Nm2C-2
m = 9.1 ´ 10-31
kg
r1=
?
p
= ?
L
= ?
K.E = ?
P.E
= ?
Total
Energy = E = ?
20.2 What are the energies in eV of quanta of wavelength? l = 400, 500 and 700 nm. 12120027
Data: la
= 400 nm = 400 ´ 10-9 m
lb
= 500 nm = 500 ´ 10-9 m
lc
= 700 nm = 700 ´ 10-9 m
c = 3 ´ 108
m/sec
Ea= ?
Eb= ?
Ec= ?
20.3 An electron jumps from a
level Ei= - 3.5 ´ 10-19J
to Ef = - 1.20 ´ 10-18
J. What is the wavelength of the emitted light?
(Board
2010, 14)12120028
Data: Ei= -3.5 ´ 10-19 J
Ef= -1.20 ´ 10-18 J
h
= 6.62 ´
10-34Js
c
= 3 ´
108 m/sec
l = ?
20.4 Find the wavelength of
the spectral line corresponding to the transition in hydrogen from n = 6 state
to n = 3 state. (Board 2013) 12120029
Data: n = 6
p= 3
RH =
1.097 ´
107m-1
l = ?
20.5 Compute the shortest
wavelength radiation in the Balmer series? What value of n must be used? (Board 2015, 16) 12120030
Data: RH = 1.097 ´ 10-7m-1
lmin (in Balmer
series) = ?
p=
2 ,
n = ¥
20.6 Calculate the longest
wavelength of radiation for the Paschen series. 12120031
Data: RH = 1.097 ´ 107
m-1
n = 4
p=
3
lmax
= ?
20.7 Electron in an X-ray tube
are accelerated through a potential difference of 3000 V. If these electrons
were slowed down in a target, what will be the minimum wavelength of X-rays
produced?
12120032
Data: V = 3000 volt
c
= 3 ´
108ms-1
h
= 6.62 ´
10-34 Js
lmin
= ?
e
= 1.6 ´
10-19
20.8 The wavelength of K-X-ray
from copper is 1.377 ´ 10-10
m. What is the energy difference between the two levels from which this
transition results? 12120033
Data: l =
1.377 ´
10-10 m
h = 6.62 ´ 10-34Js
c
= 3 ´
108 m/s
DE = ?
20.9 A tungsten target is
struck by electrons that have been accelerated from rest through 40KV potential
difference. Find the shortest wavelength of the bremsstrahlung radiation
emitted.12120034
Data: V = 40 KV
= 40 ´ 103
V
h
= 6.62 ´
10-34Js
c
= 3 ´
108 ms-1
e = 1.6 ´ 10-19C
l = ?
20.10 The orbital electron of a
hydrogen atom moves with a speed of
5.456 ´ 105 ms-1.
(a) find the value of the quantum number ‘n’ associated with this electron, (b)
calculate the radius of this orbit, and (c) Find the energy of the electron in
this orbit. 12120035
Data: vn = 5.456 ´ 105
ms-1
h
= 6.62 ´
10-34Js
k
= = 9 ´ 109 Nm2C-2
e
= 1.6 ´
10-19 C
m
= 9.1 ´
10-31 kg
n
= ?
rn = ?
En =?
b.
|
Unit |
NUCLEAR PHYSICS |
|
21 |
Q.1 What is atomic Nucleus? Define its mass number and charge numbers? 12121001
Q.2 What are isotopes? (Board 2016) 12121002
Q.3 How isotopes are detected with a mass
spectrograph? Describe construction and working of Mass spectrograph. (Board 2015,
16) 12121003
Q.4 Explain the term “mass defect” and binding energy” with the help of
examples. 12121004
(Board 2013)
Q.5 What is meant by the term radioactivity? Give an account of the
radiations emitted by radioactive substance. 12121005
Q.6 What is phenomenon of nuclear transmutation or radioactive decay?
Explain. 12121006
Q.
7. How b-particle
comes from nucleus? 12121007
Q.8 What is meant by half-life of a
radioactive element? How can half-life of radioactive element be determined
from radioactive decay? 12121008
Q.9 Write a brief account of interaction of a-particle
with matter? 12121009
Q.10 Write brief account of interaction of b-particles
with matter? 12121010
Q.11 Give a brief account of interaction of g-rays
with matter. 12121011
Q.12 Give brief account of interaction of neutrons with matter. 12121012
Q.13 What is radiation detectors? Discuss the principle, construction
and working Wilson cloud
chamber for detecting nuclear radiation. 12121013
Q.14 Describe the principle, construction and working of Geiger Muller
counter. 12121014
Q.15 Describe Construction, working of solid
state detector. 12121015
Q.16 What are nuclear reaction? Explain. 12121016
Q.17 What do you understand by nuclear fission? 12121017
Q.18 What is fission chain reaction? Describe controlled fission chain
reaction and uncontrolled
fission chain reaction. 12121018
Q.19 What
is meant by critical mass? What role does it play in fission chain reaction?
12121019
Q.20 Describe the principle, construction and working of nuclear
reactor with the help of diagram. (Board 2014) 12121020
Q.21 Describe types of reactor. 12121021
Ans: Types
of Reactors:
Q.22 State and explain nuclear fusion reaction. 12121022
Ans: Nuclear
Fusion
Q.23 Describe nuclear reaction taking place in
the sun. 12121023
Q.24 Write comprehensive note on radiation
exposure and it damages. 12121024
Q.25 What are the biological effects of
radiation? 12121025
Q.26 What are the tracer techniques? Explain what
is their use in agriculture diagnosis and therapy. 12121026
Q.27 What is meant by radiography? Explain 12121027
Q.28 What are basic forces of nature? Discuss
their unification. 12121028
Q.29 Explain building blocks of matter. 12121029
SHORT
QUESTIONS
21.1 What
are isotopes? What do they have in common and what are their differences? 12121030
21.2 Why
are heavy nuclei un-stable?
(Board 2010, 15)12121031
21.3 If
a nucleus has a half-life of 1 year, does this mean that it will be completely
decayed after 2 years? Explain.
(Board 2015) 12121032
21.4
What fraction of a radioactive sample decays after two half-lives have elapsed? 12121033
21.5 The
radioactive element Ra has a half-life of 1.6 ´ 103 years. Since the Earth is about 5 billion
years old, how can you explain why we still can find this element in nature? 12121034
21.6 Describe
a brief account of interaction of various types of radiations with matter. 12121035
21.7 Explain
how a-and b-particles may ionize an atom without directly hitting
the electrons? What is the difference in the action of the two particles for
producing ionization? 12121036
21.8 A
particle which produces more ionization is less penetrating, why?
(Board 2014,
15)12121037
21.9 What
information is revealed by the length and shape of the tracks of an incident
particle in Wilson cloud chamber? 12121038
21.10 Why
must a Geiger muller tube for detecting a-particles
have a very thin end window? Why does a Geiger Muller tube for detecting g-rays not need a window at all? 12121039
21.11 Describe the principle of operation of a
solid state detector of ionizing radiation in terms of generation and detection
of charge carriers. 12121040
21.12 What
do we mean by the term critical mass? (Board 2013,
14) 12121041
21.13 Discuss
the advantages and dis-advantages of nuclear power compared to the use of
fossil fuel generated power.
12121042
21.14 What
factors make a fusion reaction difficult to achieve?
(Board 2013,
14)12121043
21.15 Discuss
the advantages and disadvantages of fusion power from the point of safety,
pollution and resources.
Ans. (Board 2015) 12121044
21.16 What do you understand by “background radiation”?
State two sources of this radiation.
(Board
2013, 14, 16) 12121045
21.17 If
someone swallowed an α and a b-source,
which would be the more dangerous to you? Explain why?
(Board 2013)12121046
21.18 Which
radiation dose would deposit more energy to the body (a) 10 mGy to the hand, or
(b) 1mGy dose to your entire body. 12121047
21.19 What
is a radioactive tracer? Describe one application each in medicine, agriculture
and industry. 12121048
21.20 How
can radioactivity help in the treatment of cancer? (Board 2014, 16) 12121049
Solved Examples
Example 1: (Board 2016) 12121050
Find the
mass defect and binding energy of the deuteron nucleus. The experimental mass
of deuteron is 3.3435 ´ 10-27kg.
Example 2: 12121051
Iodine-131
is an artificial radioactive isotope. It is used for the treatment of human
thyroid gland. Its half-life is 8 days. In the drug store of a hospital 20 mg
of iodine-131 is present. It was received from the laboratory 48 days ago. Find
the quantity of iodine-131 in the hospital after this period.
Example 3: 12121052
How much energy is absorbed by a man of mass 80 kg who receives a lethal whole body equivalent dose of 400 rem in the form of low energy neutrons for which RBE factor is 10?
PROBLEMS
21.1 Find the mass defect and the binding energy
for tritium, if the atomic mass of tritium is 3.016049u.
(Board 2013) 12121053
Data
mass of tritium nucleus=m=3.016049 u
Mass of proton =mp = 1.007276u
Mass of neutron =mn =
1.008665u
a) Mass
defect =
m=?
b) Binding
energy =B.E= ?
21.2 The half-life of 
is 9.70 hours. Find its decay constant. (Board 2013)12121054
Data:
= 9.70 hour = 4920s
21.3 The element 
is unstable and decays by b-ray
emission with a half- life 6.66 hours. State the nuclear reaction and the
daughter nuclei. 12121055
Data
Half-life
= T1/2 = 6.66 ´ 60 ´ 60
= 23976 sec.
Nuclear
reaction = ?
Daughter
Nucleus = ?
21.4 Find the
energy associated with the following reaction:(Mass of 
= 1.007844)
12121056
N + 
+ 
What
does negative sign indicate?
Data:
Mass of N = 14.0031u
Mass of = 4.00264u
Mass of = 16.991u
Mass of = 1.0073u
Energy associated
= Q = ?
21.5 Determine the energy associated with the
following reaction:
(Mass
of 
= 14.00774) 12121057
+ 
Data:
Mass
of = 14.003918u
Mass
of 
= 14.0067u
Mass
of = 0.000548u
Energy associated
= Q = ?
21.6 If 
decays twice by a-emission,
what is the resulting isotope?
(Board 2014, 15)12121058
21.7 Calculate the energy (in MeV) released in
the following fusion reaction:
12121059
Data:
Mass of 
= 2.014102u
Mass of 
= 3.01605u
Mass of 
= 4.00263u
Mass of 
= 1.008665u
Energy released =
Q = ?
21.8 A Sheet of lead 5.0 mm thick reduces the
intensity of a beam of g-rays
by a factor 0.4. Find half value thickness of lead sheet which will reduce the
intensity to half of its initial value. 12121060
Data:
Thickness of the sheet = x1
= 5mm
= 5 
10-3m
Initial intensity of g-rays
beam = I1 = 0.4 I 0
final intensity of g-rays
beamI2 = 0.5 I 0
thickness of the sheet = x2= ?
21.9 Radiation from a point source obeys the
inverse square law. If the count rate at a distance of 1.0m from Geiger counter
is 360 counts per minute, what will be its count rate at 3.0m from the source?
12121061
Data:
The initial count rate = I1
= 360 counts / min
Initial distance of source from GM.
Counter = r1 = 1.0m
Final distance of source from GM.
Counter = r2 = 3.0m
Final count rate =
I2=?
21.10 A 75kg person receives a whole body radiation
dose of 24 m rad, delivered by a-particles
for which RBE factor is 12. Calculate (a) the absorbed energy in joules, and
(b) the equivalent dose in rem.
12121062
Data:
Mass of the body =
m = 75kg
Absorbed dose = D
= 24m rad
= 24 10-3
rad
as 1
rad = 0.01 Gy
\ D = 24 ´
10-3´
0.01
= 24 ´ 10-5Gy
RBE factor of
radiation = 12
a) Energy
absorbed in joules = E = ?
b) Equivalent
dose De in rem = ?
