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Reversing Magnetic Field and Current
Figure 13 shows a wire held between two magnets. The wire forms part of a closed circuit connected to an ammeter.
The teacher moved the wire upwards between the magnets. The needle on the ammeter deflected to a value of +0.4 mA and then returned to zero.
What was the deflection of the needle on the ammeter? Tick one box.
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Marking points
- 1 Selects ‘The needle will deflect to −0.4 mA.’
Why this answer loses marks
Reversing the magnetic field stops the induction.
The wire still cuts a field, so the induced response remains; reversing one direction reverses current direction while unchanged conditions preserve magnitude.