Electromagnetic Induction - Online Test

Q1. A rectangular conductor PQRS in which the conductor PQ is free to move is kept in a magnetic field B ,which is perpendicular to the PQRS which lies in a single plane. If the conductor PQ has a length l,moves with a speed v, then induced emf is
Answer : Option B
Explaination / Solution:

e=dϕdt=d(BS)dt=B.dsdt=Bl.dxdt=Blv
Q2. A moving conductor rod is 0.10 m long, and moves with a velocity of 2.5 m/s perpendicular to the magnetic field B of 0.60 T. If the circuit is completed with a resistance of 0.03Ω. Find the motional emf and the induced current.
Answer : Option B
Explaination / Solution:

e = Bvl = 0.60 x 2.5 x 0.1 = 0.15V


Q3. A rectangular conductor PQRS in which the conductor PQ is free to move is kept in a magnetic field B ,which is perpendicular to the PQRS which lies in a single plane. If the conductor PQ of length l is pushed by a force F then the power supplied is (assuming a circuit ressistance r)
Answer : Option D
Explaination / Solution:

P = Fv



Q4. A rectangular conductor PQRS in which the conductor PQ is free to move is kept in a magnetic field B ,which is perpendicular to the PQRS which lies in a single plane. If the conductor PQ of length l is pushed by a force F and circuit has resistance r,the power loss in the resistance is
Answer : Option B
Explaination / Solution:



Q5. Eddy Currents are
Answer : Option D
Explaination / Solution:

Eddy currents (also called Foucault currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. By lenz's law an eddy current creates a magnetic field that opposes a change in the magnetic field that created it, and thus eddy currents react back on the source of the magnetic field.

Q6. Damping in galvanometers is based on
Answer : Option D
Explaination / Solution:

The coil of galvanometer is wound on a light metal frame. When the coil and frame rotate in the field of the permanent magnet, the eddy current set up in the frame oppose the motion so that the coil returns to zero quickly.

Q7. If current in a coil is changing with time, relationship of current to emf is described by
Answer : Option C
Explaination / Solution:



Q8. There are two stationary coils near each other. If current in coil-1 is changing with time, relationship of current in coil-2 to it's emf is described by
Answer : Option D
Explaination / Solution:


M is mutual inductance


Q9. The self-inductance of a long solenoid, the core of which consists of a magnetic material of permeability μr,turns per unit length n,length l and area A is given by
Answer : Option A
Explaination / Solution:


N = total no. of turns

if n = no. of turns per unit length then

N = nl


Q10. An AC generator consists of
Answer : Option D
Explaination / Solution:

AC generators operate on the same fundamental principles of electromagnetic induction.The turning of a coil in a magnetic field produces motional emfs in both sides of the coil. A slip ring is a method of making an electrical connection through a rotating assembly. Formally, it is an electric transmission device that allows energy flow between two electrical rotating parts, such as in a motor.