Electromagnetic Induction- 2 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A current increases uniformly from zero to one ampere in
0.01 second, in a coil of inductance 10 mH. The induced
e.m.f. will be -
(a) 1 V (b) 2 V (c) 3 V (d) 4 V
Q.2 The current in a coil varies with respect to time t as I = 3t
2
 +
2t. If the inductance of coil be  10 mH, the value of induced
e.m.f. at t = 2s will be-
(a) 0.14 V (b) 0.12 V (c) 0.11 V (d) 0.13 V
Q.3 Two circular coils can be arranged in any of the three
situations shown in the figure. Their mutual inductance will
be
(A) (B)
(C)
(a) Maximum in situation (A)
(b) Maximum in situation (B)
(c) Maximum in situation (C)
(d) The same in all situations
Q.4 A current of 10 A in the primary coil of a circuit is reduced
to zero at a uniform rate in 10
–3
 second. If the coefficient
of mutual inductance is 3H, the induced e.m.f. in the
secondary coil will be-
(a) 3 kV (b) 30 kV (c) 2 kV (d) 20 kV
Page 2


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A current increases uniformly from zero to one ampere in
0.01 second, in a coil of inductance 10 mH. The induced
e.m.f. will be -
(a) 1 V (b) 2 V (c) 3 V (d) 4 V
Q.2 The current in a coil varies with respect to time t as I = 3t
2
 +
2t. If the inductance of coil be  10 mH, the value of induced
e.m.f. at t = 2s will be-
(a) 0.14 V (b) 0.12 V (c) 0.11 V (d) 0.13 V
Q.3 Two circular coils can be arranged in any of the three
situations shown in the figure. Their mutual inductance will
be
(A) (B)
(C)
(a) Maximum in situation (A)
(b) Maximum in situation (B)
(c) Maximum in situation (C)
(d) The same in all situations
Q.4 A current of 10 A in the primary coil of a circuit is reduced
to zero at a uniform rate in 10
–3
 second. If the coefficient
of mutual inductance is 3H, the induced e.m.f. in the
secondary coil will be-
(a) 3 kV (b) 30 kV (c) 2 kV (d) 20 kV
2
DPP/ P 45
Q.5 Three inductances are connected as shown  below.
Assuming no coupling, the resultant inductance will be-
(L
1
 = 0.75 H, L
2
 = L
3
 = 0.5 H)
(a) 0.25 H
(b)    0.75 H
(c) 0.01 H
L
1
L
2
L
3
(d)    1 H
Q.6 A solenoid has an inductance of 50 mH and a resistance of
0.025 W. If it is connected to a battery, how long will it
take for the current to reach one half of its final equilibrium
value?
(a) 1.34 s (b) 1.38 s (c) 1.38 ms (d) 0.23 s
Q.7 The current in the primary coil of a transformer (assuming
no power loss) as shown in fig. will be –
(a) 0.01 A
(b) 1.0 A
(c) 0.1 A
/\/\/\/
P
S
V
P 
= 220 V
220 W
S P (d) 10
–6
 A.
Q.8 A current of 5A is flowing at 220V in the primary coil of a
transformer. If the voltage produced in the secondary coil
is 2200V and 50% of power is lost, then the current in the
secondary coil will be –
(a) 2.5A (b) 5A (c) 0.25A (d) 0.025A
Q.9 An inductor (L = 100 mH), a resistor (R = 100 W) and a
battery (E = 100 V) are initially connected in series as
shown in the figure. After a long time the battery is
disconnected after short circuiting the points A and B. The
current in the circuit 1 ms after the short circuit is
(a) e A
A B
R
L
E
(b) 0.1 A
(c) 1 A
(d) 1/e A
Q.10 Which of the following is constructed on the principle of
electromagnetic induction ?
(a) Galvanometer (b) Electric motor
(c) Generator (d) Voltmeter
Q.11 In the circuit, E = 10 volt, R
1
 = 5.0 ohm, R
2
 = 10 ohm and
L = 5.0 henry . The current just after the switch S is pressed
is.
L
(a) 2.0A (b) 3.0A
(c) 5.0A (d) 6.0A
Q.12 Two inductors L
1
 and L
2
 are at a sufficient distance apart.
Equivalent inductance when they are connected (i) in series
(ii) in parallel are
(a)L
1
 + L
2
, 
12
12
LL
LL +
(b)L
1
 – L
2
, 
12
12
LL
LL -
(c)L
1
 L
2
, 
12
12
LL
LL
+
(d) None of these
Q.13 A small coil of N
1
 turns, l
1
 length is tightly wound over the
centre of a long solenoid of length l
2
, area of cross-section
A and number of turns N
2
. If a current I flows in the small
coil, then the flux through the long solenoid is
(a) zero (b)
2
01
1
N AI m
l
(c) inifinite (d)
0 12
2
N N AI m
l
Q.14If the current in the primary coil is reduced from 3.0
ampere to zero in 0.001 second, the induced e.m.f in the
secondary coil is 1500 volt. The mutual inductance of the
two coils will be-
(a) 0.5 H (b) 0.05 H (c) 0.005 H (d) 0.0005 H
Q.15 A 50 Hz a.c. current of crest value 1A flows through the
primary of a transformer. If the mutual inductance between
the primary and secondary be 1.5 H, the crest voltage
induced in secondary is-
(a) 75 V (b) 150 V (c) 471 V (d) 300 V
Q.16 In an inductor of inductance L = 100 mH, a current of I =
10A is flowing. The energy stored in the inductor is
(a) 5 J (b) 10 J (c) 100 J (d) 1000 J
Page 3


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A current increases uniformly from zero to one ampere in
0.01 second, in a coil of inductance 10 mH. The induced
e.m.f. will be -
(a) 1 V (b) 2 V (c) 3 V (d) 4 V
Q.2 The current in a coil varies with respect to time t as I = 3t
2
 +
2t. If the inductance of coil be  10 mH, the value of induced
e.m.f. at t = 2s will be-
(a) 0.14 V (b) 0.12 V (c) 0.11 V (d) 0.13 V
Q.3 Two circular coils can be arranged in any of the three
situations shown in the figure. Their mutual inductance will
be
(A) (B)
(C)
(a) Maximum in situation (A)
(b) Maximum in situation (B)
(c) Maximum in situation (C)
(d) The same in all situations
Q.4 A current of 10 A in the primary coil of a circuit is reduced
to zero at a uniform rate in 10
–3
 second. If the coefficient
of mutual inductance is 3H, the induced e.m.f. in the
secondary coil will be-
(a) 3 kV (b) 30 kV (c) 2 kV (d) 20 kV
2
DPP/ P 45
Q.5 Three inductances are connected as shown  below.
Assuming no coupling, the resultant inductance will be-
(L
1
 = 0.75 H, L
2
 = L
3
 = 0.5 H)
(a) 0.25 H
(b)    0.75 H
(c) 0.01 H
L
1
L
2
L
3
(d)    1 H
Q.6 A solenoid has an inductance of 50 mH and a resistance of
0.025 W. If it is connected to a battery, how long will it
take for the current to reach one half of its final equilibrium
value?
(a) 1.34 s (b) 1.38 s (c) 1.38 ms (d) 0.23 s
Q.7 The current in the primary coil of a transformer (assuming
no power loss) as shown in fig. will be –
(a) 0.01 A
(b) 1.0 A
(c) 0.1 A
/\/\/\/
P
S
V
P 
= 220 V
220 W
S P (d) 10
–6
 A.
Q.8 A current of 5A is flowing at 220V in the primary coil of a
transformer. If the voltage produced in the secondary coil
is 2200V and 50% of power is lost, then the current in the
secondary coil will be –
(a) 2.5A (b) 5A (c) 0.25A (d) 0.025A
Q.9 An inductor (L = 100 mH), a resistor (R = 100 W) and a
battery (E = 100 V) are initially connected in series as
shown in the figure. After a long time the battery is
disconnected after short circuiting the points A and B. The
current in the circuit 1 ms after the short circuit is
(a) e A
A B
R
L
E
(b) 0.1 A
(c) 1 A
(d) 1/e A
Q.10 Which of the following is constructed on the principle of
electromagnetic induction ?
(a) Galvanometer (b) Electric motor
(c) Generator (d) Voltmeter
Q.11 In the circuit, E = 10 volt, R
1
 = 5.0 ohm, R
2
 = 10 ohm and
L = 5.0 henry . The current just after the switch S is pressed
is.
L
(a) 2.0A (b) 3.0A
(c) 5.0A (d) 6.0A
Q.12 Two inductors L
1
 and L
2
 are at a sufficient distance apart.
Equivalent inductance when they are connected (i) in series
(ii) in parallel are
(a)L
1
 + L
2
, 
12
12
LL
LL +
(b)L
1
 – L
2
, 
12
12
LL
LL -
(c)L
1
 L
2
, 
12
12
LL
LL
+
(d) None of these
Q.13 A small coil of N
1
 turns, l
1
 length is tightly wound over the
centre of a long solenoid of length l
2
, area of cross-section
A and number of turns N
2
. If a current I flows in the small
coil, then the flux through the long solenoid is
(a) zero (b)
2
01
1
N AI m
l
(c) inifinite (d)
0 12
2
N N AI m
l
Q.14If the current in the primary coil is reduced from 3.0
ampere to zero in 0.001 second, the induced e.m.f in the
secondary coil is 1500 volt. The mutual inductance of the
two coils will be-
(a) 0.5 H (b) 0.05 H (c) 0.005 H (d) 0.0005 H
Q.15 A 50 Hz a.c. current of crest value 1A flows through the
primary of a transformer. If the mutual inductance between
the primary and secondary be 1.5 H, the crest voltage
induced in secondary is-
(a) 75 V (b) 150 V (c) 471 V (d) 300 V
Q.16 In an inductor of inductance L = 100 mH, a current of I =
10A is flowing. The energy stored in the inductor is
(a) 5 J (b) 10 J (c) 100 J (d) 1000 J
DPP/ P 45
3
Q.17 A step up transformer has transformation ratio 5 : 3. What
is voltage in secondary if voltage in primary is 60 V
(a) 20 V (b) 60 V (c) 100 V (d) 180 V
Q.18 A transformer has turn ratio 100 : 1. If secondary coil has
4 amp current then current in primary coil is
(a) 4 A (b) 0.04 A (c) 0.4 A (d) 400 A
Q.19 A step-down transformer is used on a 1000 V line to deliver
20 A at 120 V at the secondary coil. If the efficiency of
the transformer is 80%, the current drawn from the line
is:
(a) 3 A (b) 30 A (c) 0.3 A (d) 2.4 A
Q.20 Energy stored in an inductor is proportional to (i = current
in the inductor)
(a) i (b) i (c) i
2
(d) i
3
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.21Voltage (r. m. s) in the secondary coil of a transformer
depends upon
(1) voltage in the primary coil
(2) ratio of number of turns in the two coils
(3) frequency of the source
(4) time-period of the source
Q.22 Core of a transformer can’t be made up of
(1) steel (2) alnico (3) iron (4) soft iron
Q.23 Large transformer, when used for some time, become hot
and are cooled by circulating oil. The heating of
transformer is due to
(1) heating effect of current
(2) hysteresis loss
(3) chemical effect of current
(4) magnetic effect of current
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
In Fig., there is a conducting loop ABCDEFA, of resistance l
per unit length placed near a long straight current-carrying wire.
The dimensions are shown in the figure. The long wire lies in
the plane of the loop. The current in the long wire varies as I = I
0
t.
E
D
C
a
a
a
a
F
A B
l
I
Q.24 The mutual inductance of the pair is
(a)
0
a 2a
1n
2
m + æö
ç÷
p
èø
l
l
(b)
0
a 2a
1n
2
m - æö
ç÷
p
èø
l
l
(c)
0
2a a
1n
m + æö
ç÷
p
èø
l
l
(d)
0
a a
1n
m + æö
ç÷
p
èø
l
l
Q.25 The e.m.f. induced in the closed loop is
(a)
00
Ia 2a
1n
2
m + æö
ç÷
p
èø
l
l
(b)
00
Ia 2a
1n
2
m - æö
ç÷
p
èø
l
l
(c)
00
2 Ia a
1n
m + æö
ç÷
p
èø
l
l
(d)
00
Ia a
1n
m + æö
ç÷
p
èø
l
l
Q.26 The heat produced in the loop in time t is
(a)
2
0
0
a
1n I at
2
4
mé +ù æö
ç÷ êú
p
èø ëû
l
l
l
(b)
2
0
0
2a
1n I at
2
8
mé +ù æö
ç÷ êú
p
èø ëû
l
l
l
(c)
2
0
0
2 a
1n I at
3
m é +ù æö
ç÷ êú
p
èø ëû
l
l
l
(d)
2
0
0
3a
1n I at
2
6
mé +ù æö
ç÷ êú
p
èø ëû
l
l
l
Page 4


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A current increases uniformly from zero to one ampere in
0.01 second, in a coil of inductance 10 mH. The induced
e.m.f. will be -
(a) 1 V (b) 2 V (c) 3 V (d) 4 V
Q.2 The current in a coil varies with respect to time t as I = 3t
2
 +
2t. If the inductance of coil be  10 mH, the value of induced
e.m.f. at t = 2s will be-
(a) 0.14 V (b) 0.12 V (c) 0.11 V (d) 0.13 V
Q.3 Two circular coils can be arranged in any of the three
situations shown in the figure. Their mutual inductance will
be
(A) (B)
(C)
(a) Maximum in situation (A)
(b) Maximum in situation (B)
(c) Maximum in situation (C)
(d) The same in all situations
Q.4 A current of 10 A in the primary coil of a circuit is reduced
to zero at a uniform rate in 10
–3
 second. If the coefficient
of mutual inductance is 3H, the induced e.m.f. in the
secondary coil will be-
(a) 3 kV (b) 30 kV (c) 2 kV (d) 20 kV
2
DPP/ P 45
Q.5 Three inductances are connected as shown  below.
Assuming no coupling, the resultant inductance will be-
(L
1
 = 0.75 H, L
2
 = L
3
 = 0.5 H)
(a) 0.25 H
(b)    0.75 H
(c) 0.01 H
L
1
L
2
L
3
(d)    1 H
Q.6 A solenoid has an inductance of 50 mH and a resistance of
0.025 W. If it is connected to a battery, how long will it
take for the current to reach one half of its final equilibrium
value?
(a) 1.34 s (b) 1.38 s (c) 1.38 ms (d) 0.23 s
Q.7 The current in the primary coil of a transformer (assuming
no power loss) as shown in fig. will be –
(a) 0.01 A
(b) 1.0 A
(c) 0.1 A
/\/\/\/
P
S
V
P 
= 220 V
220 W
S P (d) 10
–6
 A.
Q.8 A current of 5A is flowing at 220V in the primary coil of a
transformer. If the voltage produced in the secondary coil
is 2200V and 50% of power is lost, then the current in the
secondary coil will be –
(a) 2.5A (b) 5A (c) 0.25A (d) 0.025A
Q.9 An inductor (L = 100 mH), a resistor (R = 100 W) and a
battery (E = 100 V) are initially connected in series as
shown in the figure. After a long time the battery is
disconnected after short circuiting the points A and B. The
current in the circuit 1 ms after the short circuit is
(a) e A
A B
R
L
E
(b) 0.1 A
(c) 1 A
(d) 1/e A
Q.10 Which of the following is constructed on the principle of
electromagnetic induction ?
(a) Galvanometer (b) Electric motor
(c) Generator (d) Voltmeter
Q.11 In the circuit, E = 10 volt, R
1
 = 5.0 ohm, R
2
 = 10 ohm and
L = 5.0 henry . The current just after the switch S is pressed
is.
L
(a) 2.0A (b) 3.0A
(c) 5.0A (d) 6.0A
Q.12 Two inductors L
1
 and L
2
 are at a sufficient distance apart.
Equivalent inductance when they are connected (i) in series
(ii) in parallel are
(a)L
1
 + L
2
, 
12
12
LL
LL +
(b)L
1
 – L
2
, 
12
12
LL
LL -
(c)L
1
 L
2
, 
12
12
LL
LL
+
(d) None of these
Q.13 A small coil of N
1
 turns, l
1
 length is tightly wound over the
centre of a long solenoid of length l
2
, area of cross-section
A and number of turns N
2
. If a current I flows in the small
coil, then the flux through the long solenoid is
(a) zero (b)
2
01
1
N AI m
l
(c) inifinite (d)
0 12
2
N N AI m
l
Q.14If the current in the primary coil is reduced from 3.0
ampere to zero in 0.001 second, the induced e.m.f in the
secondary coil is 1500 volt. The mutual inductance of the
two coils will be-
(a) 0.5 H (b) 0.05 H (c) 0.005 H (d) 0.0005 H
Q.15 A 50 Hz a.c. current of crest value 1A flows through the
primary of a transformer. If the mutual inductance between
the primary and secondary be 1.5 H, the crest voltage
induced in secondary is-
(a) 75 V (b) 150 V (c) 471 V (d) 300 V
Q.16 In an inductor of inductance L = 100 mH, a current of I =
10A is flowing. The energy stored in the inductor is
(a) 5 J (b) 10 J (c) 100 J (d) 1000 J
DPP/ P 45
3
Q.17 A step up transformer has transformation ratio 5 : 3. What
is voltage in secondary if voltage in primary is 60 V
(a) 20 V (b) 60 V (c) 100 V (d) 180 V
Q.18 A transformer has turn ratio 100 : 1. If secondary coil has
4 amp current then current in primary coil is
(a) 4 A (b) 0.04 A (c) 0.4 A (d) 400 A
Q.19 A step-down transformer is used on a 1000 V line to deliver
20 A at 120 V at the secondary coil. If the efficiency of
the transformer is 80%, the current drawn from the line
is:
(a) 3 A (b) 30 A (c) 0.3 A (d) 2.4 A
Q.20 Energy stored in an inductor is proportional to (i = current
in the inductor)
(a) i (b) i (c) i
2
(d) i
3
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.21Voltage (r. m. s) in the secondary coil of a transformer
depends upon
(1) voltage in the primary coil
(2) ratio of number of turns in the two coils
(3) frequency of the source
(4) time-period of the source
Q.22 Core of a transformer can’t be made up of
(1) steel (2) alnico (3) iron (4) soft iron
Q.23 Large transformer, when used for some time, become hot
and are cooled by circulating oil. The heating of
transformer is due to
(1) heating effect of current
(2) hysteresis loss
(3) chemical effect of current
(4) magnetic effect of current
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
In Fig., there is a conducting loop ABCDEFA, of resistance l
per unit length placed near a long straight current-carrying wire.
The dimensions are shown in the figure. The long wire lies in
the plane of the loop. The current in the long wire varies as I = I
0
t.
E
D
C
a
a
a
a
F
A B
l
I
Q.24 The mutual inductance of the pair is
(a)
0
a 2a
1n
2
m + æö
ç÷
p
èø
l
l
(b)
0
a 2a
1n
2
m - æö
ç÷
p
èø
l
l
(c)
0
2a a
1n
m + æö
ç÷
p
èø
l
l
(d)
0
a a
1n
m + æö
ç÷
p
èø
l
l
Q.25 The e.m.f. induced in the closed loop is
(a)
00
Ia 2a
1n
2
m + æö
ç÷
p
èø
l
l
(b)
00
Ia 2a
1n
2
m - æö
ç÷
p
èø
l
l
(c)
00
2 Ia a
1n
m + æö
ç÷
p
èø
l
l
(d)
00
Ia a
1n
m + æö
ç÷
p
èø
l
l
Q.26 The heat produced in the loop in time t is
(a)
2
0
0
a
1n I at
2
4
mé +ù æö
ç÷ êú
p
èø ëû
l
l
l
(b)
2
0
0
2a
1n I at
2
8
mé +ù æö
ç÷ êú
p
èø ëû
l
l
l
(c)
2
0
0
2 a
1n I at
3
m é +ù æö
ç÷ êú
p
èø ëû
l
l
l
(d)
2
0
0
3a
1n I at
2
6
mé +ù æö
ç÷ êú
p
èø ëû
l
l
l
4
DPP/ P 45
DIRECTIONS (Qs. 27-Q.29) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement-1 is False, Statement-2 is True.
(d) Statement-1 is True, Statement-2 is False.
Q.27 Statement-1 : Soft iron is used as a core of transformer.
Statement-2 :  Area of hysteresis loop for soft iron is
small.
Q.28Statement-1 : An electric motor will have maximum
efficiency when back e.m.f. is equal to half of the applied
e.m.f.
Statement-2 : Efficiency of electric motor depends only
on magnitude of back e.m.f.
Q.29 Statement-1 :  A transformer cannot work on dc supply.
Statement-2 :  dc changes neither in magnitude nor in
direction.