ElectromagnetsIB MYP Physics: Mind map

Exam questions on Electromagnets

1. A scrapyard in Johannesburg uses a crane with an electromagnet to lift old steel car bodies. The electromagnet is a coil of insulated copper wire wound round a soft iron core and connected to a d.c. supply.
   Explain why a soft iron core is used in the crane's electromagnet.2 marks
2. In a car, the driver's ignition switch controls the starter motor through a relay. The starter motor needs a very large current, while the circuit with the ignition switch carries only a small current.
   Explain why a relay is used to switch the starter motor instead of the driver's ignition switch.2 marks
3. A technician in Cairo makes a solenoid, which is a long coil of insulated copper wire, and connects it to a d.c. power supply through a switch. She uses a small plotting compass to investigate the magnetic field.
   Describe the magnetic field around the solenoid when a current flows, and state how the right-hand grip rule shows which end is the north pole.3 marks