Magnetic Fields (OCR A Level Physics)

Exam Questions

10 mins5 questions
1a2 marks
a)
The diagram below shows the top-view of a long current-carrying wire. wire

q19a-paper-2-nov-2021-ocr-a-level-physics

The direction of the current in the wire is into the plane of the paper.

Draw at least three field lines to indicate the magnetic field pattern around this wire.

[2]

1b4 marks
b)
The arrangement shown in the diagram below is used to determine the magnetic flux density between the poles of a permanent magnet.

q19b-paper-2-nov-2021-ocr-a-level-physics

The magnet is placed on the digital balance. The current-carrying wire is horizontal and at right angles to the magnetic field between the poles of the magnet. The wire is fixed.

The following results are collected.

•    length of the wire in the uniform field of the magnet = 6.0 ± 0.2 cm
•    balance reading with no current in wire = 80.0 g
•    balance reading with current in wire = 82.2 g
•    current in wire = 5.0 ± 0.1 A


Calculate the magnetic flux density B, including the absolute uncertainty.
Ignore the absolute uncertainty in the balance readings.
Write your value for B to 2 significant figures and the absolute uncertainty to 1 significant figure.





B
= ................................... ± ............... T [4]

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