OCR A Level Physics

Topic Questions

6.6 Electromagnetic Induction

11 mark

A flat coil has 200 turns and a cross-sectional area of 1.20 × 10–4 m2.

q12-paper-2-nov-2021-ocr-a-level-physics

The coil is placed horizontally in a uniform magnetic field. The magnetic flux density is 0.050 T.
The magnetic field is at an angle of 30.0° to the vertical.

What is the magnetic flux linkage for this coil?

  • 3.00 × 10–6 Wb turns

  • 5.20 × 10–6 Wb turns

  • 6.00 × 10–4 Wb turns

  • 1.04 × 10–3 Wb turns

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21 mark

Faraday’s law of electromagnetic induction is written below with two terms missing.

The ...................................... induced in a circuit is directly proportional to the rate of change of magnetic flux ...................................... .

What are the two missing terms?

  • current, density

  • current, linkage

  • electromotive force, density

  • electromotive force, linkage

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31 mark

A coil with 500 turns is placed in a uniform magnetic field.
The average cross-sectional area of the coil is 3.0 × 10-4 m2.
The magnetic flux through the plane of the coil is reduced from 1.8 × 10-4 Wb to zero in a time t.
The average electromotive force (e.m.f.) induced across the ends of the coil is 0.75 V.

What is the value of t?

  • 3.6 × 10–5 s

  • 2.4 × 10–4 s

  • 0.12s

  • 8.3s

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41 mark

The number of turns on the coils of four ideal iron-cored transformers A, B, C and D are shown in the table below.

Transformer Number of turns on the secondary coil Number of turns on the primary coil
A 100 100
B 50 200
C 200 50
D 500 100

Each transformer is connected in turn to an alternating 240 V supply.

Which transformer will give the largest output current?

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