# Physics Questions and Answers – Electromagnetic Inductance

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This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Electromagnetic Inductance”.

1. Give the SI unit of self-inductance.
b) Ampere
c) Henry
d) Maxwell

Explanation: The self-inductance of a coil is said to be one henry if an induced emf of one volt is set up in it when the current in it changes at the rate of one ampere per second. Self inductance is defined as the induction of a voltage in a current-carrying wire when the current in the wire itself is changing.

2. Write the dimensions of self-inductance.
a) [M3 L2 T-2 A-2]
b) [M L2 T-2 A-2]
c) [M2 L2 T-2 A-2]
d) [M L2 T2 A-2]

Explanation: Self-inductance = $$\frac {Magnetic \, flux}{Current}$$
$$\frac {[ M L^2 T^{-2} ]}{[ A^2 ]}$$
Self-inductance = [M L2 T-2 A-2]

3. Identify the factor on which self-inductance does not depend.
a) Number of turns
b) Area of cross-section
c) Permeability of the core material
d) The permittivity of the core material

Explanation: Self-inductance is directly proportional to the number of turns and the area of cross-section. The self-inductance of a solenoid increases μr times if it is wound over an iron core of relative permeability μr.
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4. Which of the following is the unit of mutual inductance?
a) VsA-2
b) V3sA2
c) V2s
d) VsA-1

Explanation: Mutual Inductance is the interaction of one coils magnetic field on another coil as it induces a voltage in the adjacent coil. Unit of Mutual inductance = $$\frac {V}{As^{-1}}$$.
SI unit = VsA-1.

5. Identify the factor on which mutual inductance does not depend.
a) Relative separation
b) The relative orientation of the two coils
c) Reciprocity
d) Permeability of the core material

Explanation: The mutual inductance of two coils is the property of their combination. It does not matter which one of them functions as the primary or the secondary coil. Hence, mutual inductance does not depend on reciprocity.
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6. Mutual inductance is called the inertia of electricity.
a) True
b) False

Explanation: Self-induction of a coil is that the property by which it tends to take care of the magnetic flux linked with it and opposes any change within the flux by inducing a current in it. This is the reason why self-induction is named inertia of electricity.

7. Calculate the mutual inductance between two coils if a current 10 A in the primary coil changes the flux by 500 Wb per turn in the secondary coil of 200 turns.
a) 10 H
b) 104 H
c) 1000 H
d) 100 H

Explanation: NΦ = MI
200 × 500 = M × 10
M = 104 H

8. What is the relative permeability of an air-core inductor, if its self-inductance increases from 0.5 mH to 50 mH due to the introduction of an iron core into it?
a) 100
b) 0.1
c) 10000
d) 0.0001

Explanation: μr = $$\frac {\mu }{\mu_0}$$
μr = $$\frac {L}{L_0}$$
μr = $$\frac {50}{0.5}$$
μr = 100

9. What is the self-inductance of the coil, if the magnetic flux of 10 microwebers is linked with a coil when a current of 5 mA flows through it?
a) 20 mH
b) 5 mH
c) 2 mH
d) 250 mH

Explanation: Self-inductance = $$\frac {Magnetic \, flux}{Current}$$
Self inductance = $$\frac {10 \times 10^{-6}}{5 \times 10^{-3}}$$
Self inductance = 2 × 10-3 H
Self inductance = 2mH

10. Determine the self-inductance of a coil, which has a magnetic flux of 50 milliwebers that is produced when a current of 5 A flows through it?
a) 1 × 10-2 Wb
b) 1 × 10-3 Wb
c) 100 Wb
d) 1 × 103 Wb

Explanation: Self-inductance = $$\frac {Magnetic \, flux}{Current}$$
Self-inductance = $$\frac {50 \times 10^{-3}}{5}$$
Self-inductance = 1 × 10-2 Wb

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