Electromagnetic Induction Test

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Electromagnetic Induction Test - 4

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Question 1
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electromagnetic induction i.e currents can be induced in coils (Select the best)

A
Only if the coil moves

B
Only if the coil moves and magnet also moves in the same direction

C
if relative motion of coil and magnet is present.

D
Only if the magnet moves

Solution

Explanation:for electromagnetic induction magnet and coil both may move but relative motion between must be present
Question 2
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Damping in galvanometers is based oUpdate Questionn

A
eddy currents generating currents in the core opposing the motion and bringing the coil to rest quickly.

B
dash pot opposing the motion of the galvanometer needle

C
needle movement being opposed by rubber touching the needle lightly

D
needle movement being opposed by oil

Solution

Explanation : 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.
Question 3
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Predict the polarity of the capacitor in the situation described by fig.

A
B ’will be positive with respect to plate ‘A ’

B
A ’will be positive with respect to plate ‘B ’.

C
Not enough information

D
No current induced

Solution

Explanation:A will become positive with respect to B because current indused is in clockwise direction
Question 4
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A circular coil of radius 8.0 cm and 20 turns is rotated about its vertical diameter with an angular speed of 50 rad s^-1 in a uniform horizontal magnetic field of magnitude 3 ×10^-2 T. If the coil resistance is 10 Ω, maximum emf induced in the coil,maximum value of current in the coil and average power loss due to Joule heating are

A
0.603 V, 0.0303 A,0.018 W

B
0.603 V, 0.0603 A,0.038 W

C
0.603 V, 0.0603 A,0.018 W .

D
0.303 V, 0.0603 A,0.018 W

Solution

e = NBA ω= 20 x 3 x 10^-2 x (3.14 x 0.08 x 0.08) x 50 = 0.603C

average power loss due to joule heating
Question 5
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An ac generator consists of 8 turns of wire, each of area A=0.0900m² , and the total resistance of the wire is 12.0 Ω. The loop rotates in a 0.500-T magnetic field at a constant frequency of 60.0 Hz. Maximum induced emf is

A
126 V

B
136 V

C
116 V

D
106 V

Solution

e = NBA ω= NBA² πn = 8 x 0.5 x 0.09 x 2 x 3.14 x 60 = 136V
Question 6
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When a bar magnet is pushed towards the coil connected in series with a galvanometer, the pointer in the galvanometer G

A
shows deflection while bar is stationary

B
oscillates

C
shows deflection while bar is in motion

D
does not move

Solution

Explanation:When bar is in motion then flux will changed hence current will be induced.
Question 7
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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
Alternating Inductance

B
Self Inductance

C
Variable Inductance

D
Mutual Inductance.

Solution

M is mutual inductance
Question 8
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A metallic rod of 1 m length is rotated with a frequency of 50 rev/s about an axis passing through the centre point O. Other end of the metallic rod slides on a Metallic ring . A constant and uniform magnetic field of 2 T parallel to the axis is present everywhere. What is the emf between the centre and the metallic ring?

A
220 V

B
314 V .

C
240 V

D
300 V

Solution

l = 1 m
= 314V
Question 9
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Coils C₁ and C₂ are stationary. C₁ connected in series with a galvanometer while C₂ is connected to a battery through a tapping key. If the tapping key is pressed and released the galvaometer

A
does not move

B
shows deflection while current in C₂ is changing .

C
oscillates

D
shows deflection while C₂ is stationary

Solution

Explanation:flux will be changed when current in C₂ is changing. Hence current will be induced in coil C₁ .
Question 10
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An AC generator consists of

A
A coil that can rotate in a permanent magnetic field and is provided with slip rings.

B
A permanent magnet rotor and a stationary coil.

C
Two stationary coils close to each other

D
A stationary coil for emf and a movable coil fed with AC

Solution

Explanation: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.