An electric current can create a heating effect and a magnetic effect. Which row gives the effect used by a relay and one use of a relay?
- Aheating effect; allowing a small current to switch on a large current
- Bheating effect; changing the voltage of an a.c. supply
- Cmagnetic effect; allowing a small current to switch on a large current
- Dmagnetic effect; changing the voltage of an a.c. supply