A student connects a small coil to a sensitive galvanometer. The student moves the coil downwards between the poles of a horseshoe magnet, as shown in Fig. ...
Question 1 Report
A student connects a small coil to a sensitive galvanometer. The student moves the coil downwards between the poles of a horseshoe magnet, as shown in Fig. 11.1.
(a) State what happens to the galvanometer reading when the coil moves downwards through the field. [1]
(b) State what happens when the coil is then moved upwards through the field. [1]
(c) Name the effect being demonstrated. [1]
(d) Explain why no reading is observed when the coil is held stationary between the poles. [2]
Answer Details
(a) Galvanometer reading when the coil moves downwards
The galvanometer deflects (shows a reading) in one direction. [1]
Moving the coil through the magnetic field causes the coil to cut through magnetic field lines, which induces an e.m.f. and drives a current through the circuit.
(b) Galvanometer reading when the coil moves upwards
The galvanometer deflects in the opposite direction to part (a). [1]
Reversing the direction of motion reverses the direction of the induced e.m.f. and therefore the direction of the induced current.
(c) Name of the effect
Electromagnetic induction. [1]
This is the process by which a changing magnetic field through a conductor (or a conductor moving through a magnetic field) induces an e.m.f.
(d) Why no reading when the coil is stationary
When the coil is held stationary between the poles, it is not cutting through any magnetic field lines. [1]
There is no change in the magnetic field through the coil, so no e.m.f. is induced and no current flows. The galvanometer reads zero. Electromagnetic induction requires relative motion between the conductor and the magnetic field. [1]
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