Electromagnetic Induction Easy Questions and Answers | Page - 2

Electromagnetic Induction

A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction 1/π (Wb/m^2→_B .The magnetic flux linked with the disc is:

1. 0.02 Wb
1. 0.06 Wb
1. 0.08 Wb
1. 0.01 Wb

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Here,
B = 1 (Wb/m²)
π

θ = 60°
Area normal to the plane of the disc
= πr²cos60° = πr²
2

Flux = B × normal area
= 0.2 × 0.2 = 0.02 Wb
2

Correct Option: A

Here,
B = 1 (Wb/m²)
π

θ = 60°
Area normal to the plane of the disc
= πr²cos60° = πr²
2

Flux = B × normal area
= 0.2 × 0.2 = 0.02 Wb
2

A conducting circular loop is placed in a uniform magnetic field of 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm/s. The induced emf in the loop when the radius is 2 cm is

1. 4.8 πμ V
1. 0.8 πμ V
1. 1.6 πμ V
1. 3.2 πμ V

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Induced emf in the loop is given by
e = - B. dA
dt

where A is the area of the loop.
e = - B. d (π r²) = - Bπ2r dr
dt dt

r = 2cm = 2 × 10^–2 m
dr = 2 mm = 2 × 10^–3
m dt = 1s
e = - 0.04 × 3.14 × 2 × 2 × 10^-2 × 2 × 10^-3 V
1

= 0.32 π × 10^–5 V
= 3.2 π ×10^–6 V
= 3.2 π μV

Correct Option: D

Induced emf in the loop is given by
e = - B. dA
dt

where A is the area of the loop.
e = - B. d (π r²) = - Bπ2r dr
dt dt

r = 2cm = 2 × 10^–2 m
dr = 2 mm = 2 × 10^–3
m dt = 1s
e = - 0.04 × 3.14 × 2 × 2 × 10^-2 × 2 × 10^-3 V
1

= 0.32 π × 10^–5 V
= 3.2 π ×10^–6 V
= 3.2 π μV

A rectangular, a square, a circular and an elliptical loop, all in the (x – y) plane, are moving out of a uniform magnetic field with a constant velocity,
→
V = vî.
The magnetic field is directed along the negative z axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

1. the circular and the elliptical loops.
1. only the elliptical loop.
1. any of the four loops.
1. the rectangular, circular and elliptical loops.

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The induced emf will remain constant only in the case of rectangular and square loops. In case of the circular and the elliptical loops, the rate of change of area of the loops during their passage out of the field is not constant, hence induced emf will not remain constant for them.

Correct Option: A

The induced emf will remain constant only in the case of rectangular and square loops. In case of the circular and the elliptical loops, the rate of change of area of the loops during their passage out of the field is not constant, hence induced emf will not remain constant for them.

A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop.
The radius of the loop is made to shrink at a constant rate of 1 mm s^–1. The induced e.m.f. when the radius is 2 cm, is

1. 2πμ V
1. πμ V
1. π μ V
  2
1. 2μ V

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Magnetic flux linked with the loop is
φ = Bπr²
|e| = dφ = B π .2r dr
dt dt

When r = 2 cm,
dr = 1 mm s^-1
dt

e = 0.025 × π × 2 × 2 × 10^–2 × 10^–3
= 0.100 × π × 10^–5 = π × 10^–6 V = π μ V

Correct Option: B

Magnetic flux linked with the loop is
φ = Bπr²
|e| = dφ = B π .2r dr
dt dt

When r = 2 cm,
dr = 1 mm s^-1
dt

e = 0.025 × π × 2 × 2 × 10^–2 × 10^–3
= 0.100 × π × 10^–5 = π × 10^–6 V = π μ V

An electron moves on a straight line path XY as shown. The abcd is a coil adjacent to the path of electron. What will be the direction of current if any, induced in the coil?

1. adcb
1. The current will reverse its direction as the electron goes past the coil
1. No current induced
1. abcd

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Current will be induced, when e^– comes closer the induced current will be anticlockwise when e^– comes farther induced current will be clockwise

Correct Option: B

Current will be induced, when e^– comes closer the induced current will be anticlockwise when e^– comes farther induced current will be clockwise