The self inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increases as
  • l and A increase
  • l decreases and A increases.
  • l increases and A decreases.
  • both l and A decrease
In lenz's law, there is conservation of
  • Charge
  • Current
  • energy
  • momentum
Match the column
mcq-on-electromagnetic-induction-1.png
  • p -> iii, q -> ii, r -> i
  • p -> i, q -> ii, r -> iii
  • p -> ii, q -> iii, r -> i
  • p -> i, q -> iii, r -> ii
If a coil of metal wire is kept stationary in a non-uniform magnetic field, then
  • an emf is induced in the coil
  • a current is induced in the coil
  • neither emf nor current is induced
  • both emf and current is induced
A conductor of length 1.0 m falls freely under gravity from a height of 10m so it cuts the lines of force of the horizontal component of the earth magnetic field of $3.5 \times 10^{-5} \ Wb /m^2$. The EMF induced in the conductor is
  • $3.6 \times 10^{-4} \ V$
  • $1.2 \times 10^{-4} \ V$
  • $8.2 \times 10^{-4} \ V$
  • $4.2 \times 10^{-4} \ V$
if the number of turns per unit length of a coil of a solenoid is doubled . its self inductance will
  • remain constant
  • be doubled
  • be halved
  • be quadrupled
Eddy currents are produced when
  • a metal is kept in varying magnetic field
  • a metal is kept in the steady magnetic field
  • a circular coil is placed in a magnetic field
  • through a circular coil current is passed.
In an inductor of self inductance L=2mH, current changes  with time according to the relation $I=t^2e^{-t}$. At what time , EMF is zero
  • 1 sec
  • 2 sec
  • 3 sec
  • 4 sec
There are two coils A and B as shown in below figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counterclockwise. B is kept stationary when A moves. We can infer that
mcq-on-electromagnetic-induction-2.png
  • there is a constant current in the clockwise direction in A
  • there is a varying current in A
  • there is no current in A
  • there is a constant current in the counterclockwise direction in A.
Calculate the induced emf in a coil of 10H inductance in which the current changes from 8  A to 3 A in .2 sec?
  • 100 V
  • 300 V
  • 250 V
  • 200 V
Assertion and Reason (a) Assertion and reason both are correct statements and reason is correct explanation for assertion. (b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. (c) Assertion is correct statement but reason is wrong statement. (d) Assertion and reason both are incorrect statements. (e) Assertion is wrong statement but reason is correct statement Assertion: An emf  E is induced in a closed loop where magnetic flux is varied. The induced  E is not a conservative field. Reason: The line integral  E .dl around the closed loop is non-zero.
  • (a)
  • (b)
  • (c)
  • (d)
  • (e)
Assertion and Reason (a) Assertion and reason both are correct statements and reason is correct explanation for assertion. (b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. (c) Assertion is correct statement but reason is wrong statement. (d) Assertion and reason both are incorrect statements. (e) Assertion is wrong statement but reason is correct statement. Assertion: The bar magnet falling vertically along the axis of the horizontal coil will be having acceleration less than g. Reason: Clockwise current induced in the coil.
  • (a)
  • (b)
  • (c)
  • (d)
  • (e)
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion. (b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. (c) Assertion is correct statement but reason is wrong statement. (d) Assertion and reason both are incorrect statements. (e) Assertion is wrong statement but reason is correct statement. Assertion: If current is flowing through a machine of iron eddy currents are produced. Reason: Change in magnetic flux through an area causes eddy currents
  • (a)
  • (b)
  • (c)
  • (d)
  • (e)
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion. (b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. (c) Assertion is correct statement but reason is wrong statement. (d) Assertion and reason both are incorrect statements. (e) Assertion is wrong statement but reason is correct statement. Assertion: Faraday’s law are consequences of conservation of energy. Reason: In a purely resistive A.C. circuit, the current lags behind the e.m.f. in phase.
  • (a)
  • (b)
  • (c)
  • (d)
  • (e)
A toroidal solenoid with an air-core has an average value of 15 cm, area of cross-section $12 \ cm^2$ and 1200 turns. The self inductance of the toroid is .
  • 4.5 mH
  • 2.3 mH
  • 4 .1 mH
  • 5 mH
A second coil of 300 turns is wound closely on the toroid above. If the current in the primary coil is increased from zero to 2 A in .05 sec, The induced EMF in the second coil will be
  • .001 V
  • .002 V
  • .023 V
  • .145 V
A magnetic field $\mathbf{B }= B_o sin \omega t \mathbf{k}$ covers a large region where a wire AB slides smoothly over two parallel conductors separated by a distance d . The wires are in the x-y plane. The wire AB (of length d) has resistance R and the parallel wires have negligible resistance. If AB is moving with velocity v, what is the current in the circuit
  • $\frac {B_0 d}{R} (vt \omega cos \omega t + vsin \omega t)$
  • $\frac {B_0 d}{R} (vt \omega sin \omega t + vcos \omega t)$
  • $\frac {B_0 d}{R} (vt \omega sin \omega t - vcos \omega t)$
  • $\frac {B_0 d}{R} (vt \omega cos \omega t - vsin \omega t)$
What is the force needed to keep the wire moving at constant velocity?
  • $\frac {B_0^2 d^2}{R}(vt \omega cos \omega t - v sin \omega t)sin \omega t$
  • $\frac {B_0^2 d^2}{R}(vt \omega cos \omega t + v sin \omega t)cos \omega t$
  • $\frac {B_0^2 d^2}{R}(vt \omega cos \omega t - v sin \omega t)cos \omega t$
  • $\frac {B_0^2 d^2}{R}(vt \omega cos \omega t + v sin \omega t)sin \omega t$
The below figure shows two identical rectangular loop (1) and (2) placed a on table with straight long current carrying conductor between them. what will be the direction of induced in loop 1 and 2 if both the looped are pulled away from conductor with the same velocity
mcq-on-electromagnetic-induction-3.png
  • clockwise , anticlockwise
  • clockwise , clockwise
  • anticlockwise , clockwise
  • anticlockwise ,anticlockwise
Will the EMF induced will be same in both the loop
  • Equal
  • Unequal
  • Can't say
  • none of the above
0 h : 0 m : 1 s

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