A current in an electric circuit may create a heating effect as well as a magnetic effect. Which row identifies the effect on which a relay depends 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