Mains electricity

Alternating potential difference

A potential difference that continually reverses its direction

Direct potential difference

A potential difference that only acts in one direction

Alternating current (ac)

An electric current which flows consistently in one direction around a circuit

Direct current (dc)

An electric current that continually reverses direction and changes size

Sources of ac (alternating current)

Power stations, ac generators, dynamos

Sources of dc (direct current)

Cells, car batteries, solar cells, dc generators

Mains electricity

An ac supply of electricity which is generated in power stations or by renewable energy resources

Domestic electricity supply

The electricity that is delivered to houses

230 V

The potential difference of domestic electricity supply in the UK

50 Hz

The frequency of domestic electricity supply in the UK

Frequency

when used to describe electricity, it is the number of times that an ac current changes direction from positive to negative to positive again

Hertz (Hz)

The SI unit for frequency

Pd (potential difference)-time graph

A graph used to display the variance of potential with time for alternating and direct current

Dc (direct current) on a pd-time graph

Direct current produces a straight, horizontal line at a constant potential difference

Ac (alternating current) on a pd-time graph

Alternating current produced a curve which alternates between positive and negative potential differences