Alternating current (a.c.) An electric current where the flow of electrons regularly reverses direction. This type of current is produced in power stations.
Ammeter An instrument used to measure electric current in amperes.
Ampere (A) The unit used to measure the strength of an electric current. Amperes, or amps, measure how many electrons pass a certain point in one second.
Battery A device that converts chemical energy into electrical energy. When a battery is connected to a circuit, a chemical reactions inside it creates an electric current that flows out of one end, around the circuit, and back to the other end of the battery.
Circuit A pathway along which an electric current can flow, for example, a wire joining a battery and a light bulb. If there is a gap in the wire, the circuit will be broken and the current will stop flowing. Switches turn electrical appliances off by breaking a connection in a circuit.
Current electricity Electricity that flows from one point to another.
Direct current (d.c.) An electric current that always flows in one direction. Batteries produce direct current.
Electric charge Atoms are made up of subatomic particles called protons, neutrons and electrons. Electrons have a negative (-) electric charge and protons have a positive (+) electric charge. Neutrons have no charge at all.
Electric conductor A substance that electricity can easily flow through. Metals are good conductors because metal atoms contain electrons that are free to move.
Electric current The flow of electric charge through a conductor.
Electric insulator A material that reduces or stops the flow of electricity. Substances such as wood, most plastics, rubber and glass are good insulators because they have no, or very few, electrons that are free to move.
Electricity A form of energy made by the movement of electrons, the negatively charged particles found inside atoms. Electricity flows when electrons are free to move through a material. It is easily changed into other forms of energy and is easy to use because it can be directed along wires.
Electromagnet A temporary magnet produced by sending an electric current along a coil of wire that surrounds a piece of magnetic metal. The magnet can be turned on and off by switching the electricity on and off.
Electromagnetism The link between electricity and magnetism.
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