ELECTROMAGNETIC INDUCTION
2 marks · EasyExplain why no voltage is produced in a wire if it is held still in a magnetic field and why a voltage is produced when the wire is moved.
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No voltage is produced when the wire is still because there is no cutting of magnetic field lines, so no electromagnetic induction occurs. When the wire is moved, it cuts across the magnetic field lines, producing a voltage.
Common mistakes: Saying a voltage is always produced if a magnetic field is present; Not mentioning field lines being cut
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Marking points
B1 · 1 mark · States no voltage produced if wire is stationary as no field lines are cut.
B1 · 1 mark · States that voltage is produced only when wire moves and cuts field lines.
Worked solution
If the wire is held still, it does not cut any magnetic field lines, so no voltage is produced. When the wire is moved through the field, it cuts the field lines and a voltage is induced.