Category: Electromagnetism

a) The force on XY is acting downwards.
Applying Fleming’s Left Hand Rule, the middle finger points into the page, in the direction of the current flow from X to Y, the index finger points to the right, in the direction of the magnetic field, the thumb will be pointing downwards, which represents the direction of the force on XY.
b) (i) Pan moves upwards.
b) (ii) When the magnets are brought closer together, the magnetic field strength of the magnet increases, increasing downwards force on XY. The greater clockwise moment will then cause the pan to tilt upwards.
c) (i) When an alternating current flows through the iron bar, a rate of change of magnetic field is produced by the iron bar. The rate of change of magnetic field produced an induced electromotive force in the flat coil, and hence an induced current flow through the closed circuit of the coil, causing the lamp to light up.
c) (ii) The lamp will be dimmer.
The lower frequency produced a lower rate of change of magnetic field, which produce a lower electromotive force in the flat coil, causing the voltage supplied to lamp to decrease.