An electric current can cause both a heating effect and a magnetic effect. Which row identifies 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