Electricity

When electrons flow along a wire or other conductor, jumping from atom to atom, we say they make an electric current, or a flow of electricity. Because the charge on one electron is small it takes a lot of electrons to make a current.

If the current is to keep flowing there must be a source of electrons and a sink into which they flow. These could be the plates within a battery or the core winding in a dynamo.

Electricity has been with us ever since humans first appeared on Earth, in the form of lightening for example, and they created electricity by rubbing materials together. The first machine to generate an electric spark was built about 1650, and worked by rubbing a hand on a spinning sulfur ball. Electrified by friction, the sphere alternately attracted and repulsed light objects from the floor.