Class 12 Electromagnetic Induction CBSE Questions & Answers

Class 12 · Electromagnetic Induction

This is Physics Class 12 Electromagnetic Induction CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
Damping in galvanometers is based on
  • A
    needle movement being opposed by oil
  • B
    eddy currents generating currents in the core opposing the motion and bringing the coil to rest quickly.
    Correct
  • C
    dash pot opposing the motion of the galvanometer needle
  • D
    needle movement being opposed by rubber touching the needle lightly
2
If current in a coil is changing with time, relationship of current to emf is described by
  • A
    Ressistance
  • B
    Conductance
  • C
    Capacitance
  • D
    Inductance.
    Correct
3
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
  • A
    Mutual Inductance.
    Correct
  • B
    Variable Inductance
  • C
    Alternating Inductance
  • D
    Self Inductance
4
Two coils \({{\rm{C}}_{\rm{1}}}\) , \({{\rm{C}}_{\rm{2}}}\) have \({{\rm{N}}_{\rm{1}}}\) and \({{\rm{N}}_{\rm{2}}}\) turns respectively. Current \({{\rm{i}}_{\rm{1}}}\) in coil \({{\rm{C}}_{\rm{1}}}\) is changing with time. The emf in \({{\rm{C}}_{\rm{2}}}\) is given by
  • A
    \(-M\frac{di_2}{dt}\)
  • B
    \(-M\frac{di_1^2}{dt}\)
  • C
    \(-M\frac{di_1}{dt}\).
    Correct
  • D
    \(-\frac{di_1}{dt}\)
5
Two coils \({{\rm{C}}_{\rm{1}}}\) , \({{\rm{C}}_{\rm{2}}}\) have \({{\rm{N}}_{\rm{1}}}\) and \({{\rm{N}}_{\rm{2}}}\) turns respectively. Current \({{\rm{i}}_{\rm{1}}}\) in coil \({{\rm{C}}_{\rm{1}}}\) is changing with time. If \(\Phi {\rm{2}}\) is the magnetic flux through \({{\rm{C}}_{\rm{2}}}\), Mutual inductance given by
  • A
    \(\frac{i_2}{N_2\Phi_2}\)
  • B
    \(\frac{N_2\Phi_2}{i_2}\)
  • C
    \(\frac{i_1}{N_2\Phi_2}\)
  • D
    \(\frac{N_2\Phi_2}{i_1}\).
    Correct
6
When a current in a coil changes, it induces a back emf in the same coil. The self-induced emf is given by
  • A
    \(\frac{d^2I}{dt^2}\)
  • B
    \(-L\frac{dI}{dt}\).
    Correct
  • C
    \(-L\frac{dI^2}{dt}\)
  • D
    \(-L\frac{d^2I}{dt^2}\)
7
The self-inductance of a long solenoid, the core of which consists of a magnetic material of permeability μr,turns n,length l and area A is given by
  • A
    \(\mu_r \mu_0 n^2 Al^2\)
  • B
    \(\mu_0 n^2 Al\)
  • C
    \(\mu_r n^2 Al\)
  • D
    \(\mu_r \mu_0 n^2 Al\).
    Correct
8
An AC generator consists of
  • A
    Two stationary coils close to each other
  • B
    A permanent magnet rotor and a stationary coil.
  • C
    A coil that can rotate in a permanent magnet field and is provided with slip rings.
    Correct
  • D
    A stationary coil for emf and a movable coil fed with AC
9
If AC generator coil has area A, rotates in a magnetic field of B with an angular speed \(\omega \) , the voltage generated is
  • A
    varies sinusoidally.
    Correct
  • B
    varies quadratically
  • C
    is constant
  • D
    varies linearly
10
A square loop of side 20 cm and resistance \({\rm{1}}.0{\rm{ }}\Omega \) is placed vertically in the east-west plane. A uniform magnetic field of 0.10 T is set up across the plane in the north-east direction. The magnetic field is decreased to zero in 0.70 s at a steady rate. Determine the magnitudes of induced emf and current during this time-interval.
  • A
    \({\rm{NBA}}\omega {\rm{ sin}}\omega {\rm{t}}\)
    Correct
  • B
    \({\rm{BA}}\omega {\rm{ sin}}\omega {\rm{t}}\)
  • C
    \({\rm{NBA sin}}\omega {\rm{t}}\)
  • D
    \({\rm{NB}}\omega {\rm{ sin}}\omega {\rm{t}}\)
11
A circular coil of radius 10 cm, 500 turns and resistance \({\rm{2 }}\Omega \) is placed with its plane perpendicular to the horizontal component of the earth’s magnetic field. It is rotated about its vertical diameter through \({\rm{18}}0^\circ \) in 0.25 s. Estimate the magnitudes of the emf and current induced in the coil. Horizontal component of the earth’s magnetic field at the place is \({\rm{3}}.0{\rm{ }} \times {\rm{ 1}}0 - {\rm{5}}\)
  • A
    2 mv,1mA
  • B
    2 mv,2.5mA
  • C
    2 mv,2mA
    Correct
  • D
    1 mv,2mA
12
Figure shows planar loops of different shapes moving out of or into a region of a magnetic field which is directed normal to the plane of the loop away from the reader. Direction of induced current in i,ii and iii are .
  • A
    7.6 mv,2.8 mA
  • B
    7.6 mv,3.8 mA .
    Correct
  • C
    5.6 mv,2.8 mA
  • D
    7.6 mv,3.8 mA
13
A closed loop moves normal to the constant electric field between the plates of a large capacitor. Is a current induced in the loop (i) when it is wholly inside the region between the capacitor plates (ii) when it is partially outside the plates of the capacitor? The electric field is normal to the plane of the loop.
Question 13 figure 1
  • A
    clockwise, clockwise, clockwise
  • B
    anti-clockwise, clockwise, anti-clockwise
  • C
    anti-clockwise, clockwise, clockwise .
    Correct
  • D
    anti-clockwise, anti-clockwise, clockwise
14
A rectangular loop and a circular loop are moving out of a uniform magnetic field region to a field-free region with a constant velocity v. The field is normal to the loops. The time variation of emf for circular and rectangular are respectively
  • A
    (i)yes,(ii)No
  • B
    (i)yes,(ii)yes
  • C
    (i)No,(ii)No .
    Correct
  • D
    (i)No,(ii)yes
15
Polarity of the capacitor in the situation described by the adjacent figure is
Question 15 figure 1
  • A
    linear, non-linear
  • B
    on-linear, non-linear
  • C
    linear, linear
  • D
    on-linear, linear .
    Correct