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Electron flow

Each electron has only a very small amount of electric charge, and a larger unit (called the coulomb) is used when measuring practical units of charge. The charge on one electron is -1.6x10^-19 C. Usually written as e. You would need about 5x10¹⁸ electrons to have a charge of one coulomb! The electrical charge passing any one point in a circuit in one second is called the electric current, and it is measured in Amperes (A). The Amp can be defined in the following way:

A current of 1A flows in a wire if a charge of 1C passes any point in the wire each second.
Current = Charge / Time or Charge = Current x Time

An alternative definition of the ampere (amp) based on fundamental quantities is:

A current of one amp is flowing in two parallel conductors placed one metre apart in a vacuum when there is a force between them of 2x10^-7 Nm^-1.

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