How does alternating current differ from direct current?

Alternating current (AC) changes direction periodically, while direct current (DC) flows continuously in one direction.

In more detail, alternating current is a type of electrical current in which the direction of the flow of electrons switches back and forth at regular intervals or cycles. This is the type of electrical current that is delivered to homes and businesses, and it is the form of electrical energy that you typically use when you plug kitchen appliances, televisions and electric lamps into a wall socket. The standard current used in the UK is 230 volts AC at 50 cycles per second (50 Hertz).

On the other hand, direct current is an electric current flowing in one direction only. It is the simplest type of current, which is produced by sources such as batteries and fuel cells. In direct current, the electric charges flow in the same direction, distinguishing it from alternating current (AC).

The main reason for using AC in the power grid is that it is more efficient to transmit over long distances. This is because AC voltages can be readily transformed to higher or lower values. High voltages are used for long-distance transmission to reduce the loss of power, as they cause less electrical energy to be lost as heat.

In contrast, DC is used in most electronic devices, as it is a stable and continuous current. It is also used in high voltage direct current (HVDC) power transmission systems, electric vehicles, and other applications that require power to be delivered at a constant rate.

In summary, the key difference between AC and DC lies in the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, or "directly". In AC, on the other hand, electrons keep switching directions, sometimes going "forward" and then going "backward".