Question types

Electromagnetic Induction question types

164 questions across 4 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

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Sample Questions

Electromagnetic Induction questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

A current through a coil of self inductance 10 mH increases from 0 to 1 A in 0.1 s. What is the induced emf in the coil?
  • 0.1 V
  • B
    1 V
  • C
    10 V
  • D
    0.01 V

Answer: A.

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Two inductor coils with inductance 10 mH and 20 mH are connected in series. What is the resultant inductance of the combination of the two coils?
  • 20 mH
  • B
    30 mH
  • C
    10 mH
  • D
    $\frac{20}{3} mH$

Answer: A.

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A conductor rod of length (l) is moving with velocity (v) in a direction normal to a uniform magnetic field (B). What will be the magnitude of induced emf produced between the ends of the moving conductor?
  • BLv
  • B
    $BLV ^2$
  • C
    $\frac{1}{2}$ Blv
  • D
    $\frac{2 Bl }{ v }$

Answer: A.

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A circular coil of 100 turns with a cross-sectional area (A) of 1 m2 is kept with its plane perpendicular to the magnetic field (B) of 1 T. What is the magnetic flux linkage with the coil?
  • A
    1 Wb
  • 100 Wb
  • C
    50 Wb
  • D
    200 Wb

Answer: B.

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It can be shown that the mutual potential energy of two circuits is $W = Ml _1 I _2$. Therefore, the mutual inductance (M) may also be defined as the mutual potential energy (W) of two circuits corresponding to unit current flowing in each circuit.
$ M =\frac{W}{I_1 I_2}$
$M = W \left[ I _1=I_2=1\right]$
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A uniform magnetic field $B(t)$, pointing upward fills a circular region of radius, $s$ in horizontal plane. If $B$ is changing with time, find the induced electric field.
[Hint : Part of Maxwell's equation, applied to a time varying magnetic flux, leads us to the equation $\oint \vec{E} \cdot \overline{ d l}=\frac{-d \phi_m}{d t}$, where $\vec{E}$ is the electric field induced when the magnetic flux changes at the rate of $\left.\frac{d \phi_m}{d t}\right]$
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QUESTION The primary and secondary coil of a transformer each have an inductance of $200 \times 10^{-6} H$. The mutual inductance (M) between the windings is $4 \times 10^{-6} H$. What percentage of the flux from one coil reaches the other?
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An emf of $96.0\ mV$ is induced in the windings of a coil when the current in a nearby coil is increasing at the rate of $1.20\ A/s.$ What is the mutual inductance $(M)$ of the two coils?
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The value of mutual inductance of two coils is $10\ mH.$ If the current in one of the coil changes from $5\ A$ to $1\ A$ in $0.2\ s,$ calculate the value of emf induced in the other coil.
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A long solenoid has 1500 turns $/ m$. A coil C having cross sectional area 25 cm 2 and 150 turns $\left( N _{ C }\right)$ is wound tightly around the centre of the solenoid. If a current of 3.0A flows through the solenoid, calculate :
(a) the magnetic flux density at the centre of the solenoid,
(b) the flux linkage in the coil C ,
(c) the average emf induced in coil C if the direction of the current in the solenoid is reversed in a time of 0.5 s . ( $\mu_0=$ $\left.4 \pi \times 10^{-7} H / m \right)$
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A metal disc is made to spin at 20 revolutions per second about an axis passing through its centre and normal to its plane. The disc has a radius of 30 cm and spins in a uniform magnetic field of 0.20 T, which is parallel to the axis of rotation. Calculate
(a) The area swept out per second by the radius of the disc,
(b) The flux cut per second by a radius of the disc,
(c) The induced emf in the disc.
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A long solenoid of length l, cross-sectional area A and having N1 turns (primary coil) has a small coil of N2 turns (secondary coil) wound about its centre. Determine the Mutual inductance (M) of the two coils.
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A toroidal ring, having $100$ turns per cm of a thin wire is wound on a nonmagnetic metal rod of length $1\ m$ and diameter $1\ cm.$ If the permeability of bar is equal to that of free space $(\mu_0),$ calculate the magnetic field inside the bar $(B)$ when the current (i) circulating through the turns is $1\ A.$ Also determine the self-inductance $(L)$ of the coil.
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Prove that the inductance of parallel wires of length I in the same circuit is given by $L=$ $\left(\frac{\mu_0 l}{\pi}\right) \ln ( d / a )$, where $a$ is the radius of wire and $d$ is separation between wire axes.
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In a Faraday disc dynamo, a metal disc of radius R rotates with an angular velocity ω about an axis perpendicular to the plane of the disc and passing through its centre. The disc is placed in a magnetic field B acting perpendicular to the plane of the disc. Determine the induced emf between the rim and the axis of the disc.
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Calculate the value of induced emf between the ends of an axle of a railway carriage $1.75\ m$ long traveling on level ground with a uniform velocity of $50\ km$ per hour. The vertical component of Earth's magnetic field $\left(B_v\right)$ is given to be $5 \times 10^{-5} T$.
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