- An alternating current (a.c.) is one that continuously changes its direction, going back and forth around a circuit
- A direct current (d.c.) is one that is steady, constantly going the same way around a circuit, from positive to negative
Two graphs showing the variation of current with time for alternating current and direct current
- Electric cells (batteries) produce direct current (d.c.)
- Mains electricity is an alternating current
If asked to explain the difference between alternating and direct current, sketch the graphs shown above: a well-sketched (and labelled) graph can earn you full marks.