12.1 Current and Charge - created from Mind Map

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Electrical Conduction

Conventional Current

Charge Carriers

Electric current is the rate of flow of charge in the wire. This current is due to the passage of charged particles known as charge carriers.

Metals: conduction electrons carry the charge and they move around inside the metal, colliding with each other and positive metal ions.

Salt Solution: when an electric current is passed through a salt solution, the charge is carried by ions.

The direction of current in a circuits is from positive to negative.

The unit of current is the ampere (A), the symbol for current is I.

The unit of charge is the coulomb (C), the symbol is Q.

Charge flow (Q) = Current (I) x Time (t)

Eg. 5A in 200s is 1000C

Materials can be classified in electrical terms as conductors, insulators or semiconductors

Insulators: each electron is attatched to an atom and connot move away from the atom. When a voltage is applied across the insulator, no current passes through and electrons are not free to move around and carry the charge.

Metal Conductors: most electrons are attached to atoms but some are delocalised and are able to carry the charge when a voltage is applied. The electrons are attracted to the positive terminal of the metal.

Semiconductors: the number of charge carriers increases with an increase in temperature. As the temperature increases the resistance decreases.