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Electromagnetic Induction

128 Questions Start Allen Test
All Exams Allen
Q101 Allen PYQ MCQ
A 800 turn coil of effective area $0.05 \, m^{2}$ is kept perpendicular to a magnetic field $5 \times 10^{-5} \, T$ . When the plane of the coil is rotated by $90^{\circ}$ around any of its coplanar axis in 0.1 s, the emf induced in the coil will be:
A.
2 V
B.
0.2 V
C.
$2 \times 10^{-3} \, V$
D.
0.02 V
Q102 Allen PYQ MCQ
In which of the following devices, the eddy current effect is not used?
A.
induction furnace
B.
magnetic braking in train
C.
electromagnet
D.
electric heater
Q103 Allen PYQ MCQ
A cycle wheel of radius 0.5 m is rotated with constant angular velocity of 10 rad/s in a region of magnetic field of 0.1 T which is perpendicular to the plane of the wheel. The EMF generated between its centre and the rim is,
A.
0.25 V
B.
0.125 V
C.
0.5 V
D.
zero
Q104 Allen PYQ MCQ
The magnetic flux linked with a coil (in Wb) is given by the equation $\phi = 5t^{2} + 3t + 16$ The magnitude of induced emf in the coil at the fourth second will be
A.
33 V
B.
43 V
C.
108 V
D.
10 V
Q105 Allen PYQ MCQ
A wheel with 20 metallic spokes each 1 m long is rotated with a speed of 120 rpm in a plane perpendicular to a magnetic field of 0.4 G. The induced emf between the axle and rim of the wheel will be, (1 G = $10^{-4}$ T)
A.
$2.51 \times 10^{-4}$ V
B.
$2.51 \times 10^{-5}$ V
C.
$4.0 \times 10^{-5}$ V
D.
2.51 V
Q106 Allen PYQ MCQ
A step down transformer connected to an ac mains supply of 220 V is made to operate at 11V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?
A.
0.2 A
B.
0.4 A
C.
2A
D.
4A
Q107 Allen PYQ MCQ
Two conducting circular loops of radii $R_{1}$ and $R_{2}$ are placed in the same plane with their centres coinciding. If $R_{1} >> R_{2}$ , the mutual inductance M between them will be directly proportional to:
A.
$\frac{R_{1}}{R_{2}}$
B.
$\frac{R_{2}}{R_{1}}$
C.
$\frac{R_{1}^{2}}{R_{2}}$
D.
$\frac{R_{2}^{2}}{R_{1}}$
Q108 Allen PYQ MCQ
A big circular coil of 1000 turns and average radius $10\mathrm{m}$ is rotating about its horizontal diameter at $2\mathrm{rad s^{-1}}$ . If the vertical component of earth's magnetic field at that place is $2\times 10^{-5}\mathrm{T}$ and electrical resistance of the coil is $12.56\Omega$ , then the maximum induced current in the coil will be:
A.
$1.5\mathrm{A}$
B.
$1\mathrm{A}$
C.
$2\mathrm{A}$
D.
$0.35\mathrm{A}$
Q109 Allen PYQ MCQ
The magnetic flux linked to a circular coil of radius R is: $\phi = 2t^{3} + 4t^{2} + 2t + 5Wb$ The magnitude of induced emf in the coil at t = 5s is:
A.
108 V
B.
197 V
C.
150 V
D.
192 V
Q110 Allen PYQ MCQ
A 12 V, 60 W lamp is connected to the secondary of a step down transformer, whose primary is connected to ac mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding?
A.
2.7 A
B.
3.7 A
C.
0.37 A
D.
0.27 A
Q111 Allen PYQ MCQ
The magnetic energy stored in an inductor of inductance $4 \mu H$ carrying a current of 2 A is:
A.
4 mJ
B.
8 mJ
C.
8 $\mu J$
D.
4 $\mu J$
Q112 Allen PYQ MCQ
In the above diagrams, a strong bar magnet is moving towards solenoid-2 from solenoid-1. The direction of induced current in solenoid-1 and that in solenoid-2, respectively, are through the directions:
A.
AB and DC
B.
BA and CD
C.
AB and CD
D.
BA and DC
Q113 Allen PYQ MCQ
In a ideal transformer, the turns ratio $\frac{N_{p}}{N_{s}}=\frac{1}{2}$ . The ratio $V_{s}:V_{p}$ is equal to (the symbols carry their usual meaning):
A.
1:2
B.
2:1
C.
1:1
D.
1:4
Q114 Allen PYQ MCQ
Let us consider two solenoids A and B, made from same magnetic material of relative permeability $\mu_{r}$ and equal area of cross-section. Length of A is twice that of B and the number of turns per unit length in A is half that of B. The ratio of self inductance of the two solenoids, $L_{A}:L_{B}$ is:
A.
1:2
B.
2:1
C.
8:1
D.
1:8
Q115 Allen ANALYTICAL QUESTIONS MCQ
The loop shown moves with a velocity v in a uniform magnetic field of magnitude B, directed into the paper as shown in the figure. The potential difference between points P and Q is e. Then

(a) $e=\frac{1}{2}BLv$
(b) e = BLv
(c) P is positive with respect to Q
(d) Q is positive with respect to P
A.
only a is correct
B.
only a & c are correct
C.
only b is correct
D.
only b & d are correct
Q116 Allen ANALYTICAL QUESTIONS MCQ
Choose the correct options
(a) SI unit of magnetic flux is henry-ampere
(b) SI unit of coefficient of self-induction is J/A
(c) SI unit of coefficient of self-induction is $\frac{volt-second}{ampere}$
(d) SI unit of magnetic induction is weber
A.
only (a)
B.
only (b)
C.
(a) and (c)
D.
(b) and (d)
Q117 Allen ANALYTICAL QUESTIONS MCQ
In the figure shown, q is in coulomb and t in second.
At time t = 1s

(a) $V_{a} - V_{b} = 4V$
(b) $V_{b} - V_{c} = 1V$
(c) $V_{c} - V_{d} = 16V$
(d) $V_{\mathrm{a}} - V_{\mathrm{d}} = 20\mathrm{V}$
A.
only (a) is correct
B.
only (b) is correct
C.
(a), (b) and (c) are correct
D.
only (d) is correct
Q118 Allen ANALYTICAL QUESTIONS Match the Columns
A uniform but time varying magnetic field B(t) exists in a cylindrical region of radius $\alpha$ and is directed into the plane of the paper, as shown in fig. The magnetic field decreases at a constant rate inside the region. If r is the distance from the axis of the cylindrical region then match Column-I to Column-II.

Column-IColumn-II
(A)Induced electric field at point A
(B)Induced electric field at point B
(C)Force on an electron placed at point A
(D)Force on an electron placed at point B
(P)0 to 1
(Q)Zero
(R)0 to 4
(S)0 to 2
A.
A - P, B - S, C - S, D - P
B.
A - S, B - P, C - R, D - P
C.
A - P, B - Q, C - R, D - S
D.
A - P, B - P, C - R, D - R
Q119 Allen ANALYTICAL QUESTIONS Match the Columns
Match the column. Column-I to Column-II
Column-IColumn-II
(A)Magnetic field
(B)Coefficient of self induction
(C)LC
(D)Magnetic flux
(P)$[M^{1}T^{-2}A^{-1}]$
(Q)$[T^{2}]$
(R)$[ML^{2}T^{-2}A^{-2}]$
(S)None of these
A.
A - P, B - R, C - Q, D - S
B.
A - P, B - Q, C - R, D - S
C.
A - P, B - S, C - Q, D - R
D.
A - S, B - S, C - S, D - R
Q120 Allen ANALYTICAL QUESTIONS MCQ
In the circuit shown in figure, switch is closed at time t = 0. Match the following two columns.
Column-IColumn-II
(A)$V_{L}$ at t = 0
(B)$V_{R}$ at t = 0
(C)$V_{L}$ at t = 1s
(D)$V_{R}$ at t = 1s
(P)zero
(Q)10V
(R)$\frac{10}{e}V$
(S)$\left(1 - \frac{1}{e}\right)10V$
A.
A – Q, B – P, C – R, D – S
B.
A – Q, B – R, C – P, D – S
C.
A – R, B – Q, C – R, D – S
D.
A – S, B – R, C – P, D – Q
Q121 Allen ANALYTICAL QUESTIONS MCQ
Magnetic flux passing through a coil of resistance $2\Omega$ is as shown in figure. Match the following two columns. In column II all physical quantities are in SI units.
Column-IColumn-II
(A)Induced emf produced
(B)Induced current
(C)Charge flow in 2sInduced current
(D)Heat generation in 2s
(P)4
(Q)1
(R)8
(S)2
A.
A-S, B-Q, C-S, D-P
B.
A-Q, B-R, C-P, D-S
C.
A-P, B-Q, C-R, D-S
D.
A-R, B-Q, C-S, D-P
Q122 Allen ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Transformer can't be used to step up or step down the steady dc voltage
Reason (R): Transformers are based upon the principle of mutual induction for which a time varying voltage is necessary.
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q123 Allen ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The direction of induced current is always such as to oppose the change that causes it.
Reason (R) : The direction of induced current is given by Lenz's law.
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q124 Allen ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): A time varying magnetic field induces an electric field.
Reason (R) :- An inductor always tends to keep the flux constant.
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q125 Allen ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The mutual inductance of coil 1 with respect to coil 2 is the same as mutual inductance of coil 2 with respect to coil 1.
Reason (R): Mutual inductance between coils is independent of current passing through the coil
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.