Current and Charge

To make an electric current pass round a circuit, the circuit must be complete and there must be a source of potential difference, such as a battery, in the circuit. The electric current is the rate of flow of charge in the wire or the component. The current is due to the passage of charges particles. These charged particles are called charge carriers.

• In metals, the charge carriers are conduction electrons. They move about inside the metal, repeatedly colliding with each other and the fixed positve ions in the metal.
• When an electric current is passed through a salt solution, the charge is carried by ions, which are charged atoms or molecules.

The convention for the direction of current in a circuit is from positive to negative. The convention was agreed long before the discovery of electrons When it was set up, it was known that an electric current is a flow of charge one…