2.7 understand the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery.

2.7 understand the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery.

The mains electricity supply provides alternating current (a.c.). Alternating current constantly changes their direction, which is useful in electricity generator and transformers. Battery cell provide direct current (d.c.) where the current is always in the same direction.