Electromagnetic Induction (OCR A Level Physics)

A current-carrying wire of length 5.0 cm is placed perpendicular to the magnetic field.

The current I in the wire is changed and the force F experienced by the wire is measured.
Fig. 22.1 shows the graph plotted by the student.

Fig. 22.1

The student’s analysis is shown on the graph of Fig. 22.1 and in the space below.

Evaluate the information from Fig. 22.1 and the analysis of the data from the experiment. No further calculations are necessary.

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Fig. 22.2

The primary coil is connected to an alternating voltage supply. A filament lamp is connected to the output of the secondary coil.

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current = ................................. A [2]

Explain this observation.

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Fig. 21.1 shows a coil of a simple generator rotating in a uniform magnetic field.

Fig. 21.1

The coil has 85 turns of insulated wire. The cross-sectional area of the coil is 14cm².
Fig. 21.2 shows the variation of magnetic flux density B through the plane of the coil with time t as it rotates.

Fig. 21.2

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maximum e.m.f. = ...................................................... V [3]

Fig. 21.3

The magnitude of the magnetic flux density of the uniform field is now halved and the coil is rotated at twice its previous frequency.
On Fig. 21.3 sketch the new variation of the e.m.f. induced with time t.

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Fig. 5.1	Fig. 5.2

The spinning magnet induces an e.m.f. in the coil. A graph of the e.m.f. displayed on the oscilloscope screen is shown in Fig. 5.2.

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Fig. 5.3

Calculate the maximum magnetic flux through the coil using the equation

V₀ = 2π × (frequency) × (maximum magnetic flux linkage)

Give a unit with your answer.

maximum flux = ..................................... unit .............. [2]

Fig. 5.4

The student is intending to investigate how the maximum induced e.m.f. V₀ in coil Y depends on the frequency f of the alternating current in coil X.

The changing magnetic flux density in coil X induces an e.m.f. in coil Y. Faraday’s law indicates that the maximum induced e.m.f. V₀ should be directly proportional to f.

Describe how you would investigate the suggested relationship between V₀ and f in the laboratory using these coils. In your description include all of the equipment used and how you would analyse the data collected.

Use the space below to draw a suitable diagram.

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