An electromagnetic sieve shaker contains a springy iron strip attached to a tray. The iron strip, a contact P, an electromagnet, a battery and a switch are connected in series. When the strip is in its resting position, it touches contact P. The free end of the strip is close to the electromagnet, and contact P is on the opposite side of the strip from the electromagnet.
Explain why the tray vibrates repeatedly while the switch is closed.
Contact P is moved so that the strip no longer touches it when the strip is in its resting position. Explain what happens when the switch is closed.
90 exam-style questions on AQA GCSE Physics 7.2 The motor effect, covering 7.2.1 Electromagnetism, 7.2.2 Fleming's left-hand rule (HT only), 7.2.3 Electric motors (HT only), and 7.2.4 Loudspeakers (HT only). Each one has a worked solution and a mark scheme showing where the marks go.