Magnetism and Electromagnetism
4 marks · EasyA student sets up a circuit where a wire is connected to a battery and a plotting compass is placed under the wire.
What effect does turning on the current have on the compass needle? Explain your answer.
Which unit is used to measure the electric current in this circuit?
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) The compass needle moves and aligns at right angles to the wire because a magnetic field is produced around the wire when current flows.
(b) The unit for electric current is the ampere (A).
Common mistakes: Saying the compass needle points towards the battery, not perpendicular
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly states that the needle moves/aligned due to magnetic field.
B1 (a) · 1 mark · Explains that the movement is due to the magnetic field produced by the current.
B2 (b) · 2 marks · States that the unit of current is ampere (A). 1 mark for 'ampere', 1 mark for giving the symbol 'A'.
Worked solution
a) Turning on the current makes the compass needle move and align at right angles to the wire. This is because a magnetic field is produced by the current in the wire.
b) Current is measured in amperes (A).