Energy and Change Glossary

• acceleration: the rate of change of velocity with time, as an object speeds up or slows down

• alloy: a mixture of different metals; the alloy will have properties from the different metals in the mixture

• alternative energy: a form of energy which is different to the main energy source used in the country

• armature: any moving part of an electrical machine in which a current is produced by a magnetic field

• attraction: a force which causes objects to move towards each other

• battery: a group of two or more electric cells connected together

• circuit breaker: like a fuse, the circuit breaker switches off the current in the case of an electrical fault

• compression: a force which attempts to flatten or deform (squash) an object

• conductor: a substance which allows heat, sound or electric charge to pass through it easily; a good conductor allows free passage whilst a poor conductor allows partial passage

• contact force: objects are in contact with each other and exert forces on each other

• deformation: to cause an object to change its shape

• delocalised: not limited to a particular place, free to move

• earth leakage: is a circuit breaker which will switch off all the electricity to a household or business if there is an electrical fault

• earthing: a circuit is earthed when there is a direct connection to the ground; this connection is usually through the earth wire in an electrical socket

• electric cell: a system in which chemical reactions occur to generate electricity

• electric charge: the physical property of matter that causes it to experience a force when close to other electrically charged matter; there are two types of electric charges: positive and negative

• electric current: the rate of flow of charge in an electric circuit

• electric current: the rate of flow of charge

• electrical appliance: an electrical device

• electrical power: the rate at which energy is transferred

• electrode: an electric conductor used to make contact with a non-metal part of the circuit, such as a copper coin or iron nail in a lemon, or zinc or copper plates in a cell

• electrolyte: a special type of solution which is able to conduct electricity

• electrostatic force: force of attraction or repulsion between electrostatic charges

• Eskom: Electricity Supply Commission of South Africa

• estimate: a value which is not exact

• excess: more than is needed

• field forces: non-contact forces

• force: a push or a pull exerted on an object by an agent

• free-fall: when the only force acting on an object is the gravitational force

• friction: a force that opposes or tries to oppose the motion

• fuse: a safety device which switches off an appliance if the current in the circuit is too strong

• generator: a machine which produces an electric current by rotating a conducting coil in a magnetic field

• gravitational acceleration: a measure of how an object changes its speed every second; on Earth gravitational acceleration is 9,8 m/s²

• gravitational force: force of attraction between two objects because of their masses

• half cell: a setup that consists of an electrode surrounded by an electrolyte; for example, a zinc half cell could consist of a zinc metal plate (the electrode) in a zinc sulphate solution (the electrolyte)

• illegal: forbidden by law; against the law

• input energy: the energy that enters a system and is altered by the system to produce an output energy

• kilowatt-hour: a unit of energy that is useful for measuring energy consumption

• LED: light emitting diode (a diode is an electrical component that only allows current flow in one direction only and blocks the flow in the opposite direction)

• lumens: the unit of measurement for light output

• magnet: a material with a strong magnetic field around it

• magnetic force: a force exerted by a magnet on a ferromagnetic material

• magnetic material: a material which is strongly attracted to a magnet

• mass: a measure of the amount of matter making up an object

• motor: a device that can convert electrical energy into mechanical energy

• national electricity grid: the network of cables, pylons and transformers which transfer electricity throughout the country

• net force: the overall result of several forces acting on the same object at the same time

• newton: the unit of measurement of a force

• non-contact force: a force which can act over a distance without touching the object experiencing the force

• normal force: the reaction force of the surface to an object

• nuclear fission: when an atomic nucleus is split to produce two separate atomic nuclei; a large amount of energy is released during the separation

• nuclear fusion: when two small atomic nuclei are combined to produce one atomic nucleus; a large amount of energy is released as the nuclei are fused together

• nuclear power: the use of nuclear reactions to generate useful heat and electricity

• ohm: unit of measurement for resistance (Ω)

• output energy: the energy that a system produces due to an input energy

• potential difference: the difference in potential energy per charge between two points in an electric circuit

• power consumption: the amount of electrical power used by an appliance or household

• power station: a system for generating electricity

• power surge: a sudden increase in the voltage somewhere in an electric circuit which can disrupt the power supply

• provision: supplying something

• pylon: a large vertical steel tower which supports electrical power cables

• radioactive: the spontaneous release of a stream of particles or electromagnetic waves from an unstable nucleus

• rate: a ratio where one quantity is compared to time, for example km/h or m/s

• repulsion: a force that causes objects to move apart

• reset: to start something again from its start

• resistance: the opposition to the flow of electrical current through a material

• resistor: an electrical component in a circuit that opposes the flow of current in the circuit

• rheostat: a variable resistor. The amount of resistance offered by the rheostat can be adjusted

• salt bridge: a device that is used to connect the two half cells in an electric cell so that their electrolytes do not mix

• Sankey diagram: a Sankey diagram is used to show the difference between input and output energy

• series circuit: a circuit which provides only one path for electric current

• short circuit: a short circuit is a low resistance path which causes all of the current to flow through the low resistance path and not through the rest of the circuit

• speed: the rate of change of distance of an object

• survey: information gathered from a wide range of people

• tariff: the amount of money charged for every unit

• tension: the force transmitted through a rope, string or chain. It is a contact force

• tiered tariff: the amount of money charged changes if more units are used; there are different levels of tariffs

• transformer: an electrical device to transfer energy between two parts of the circuit in the national electricity grid

• transmission lines: power cables which transmit electricity across the country

• turbine: a machine which consists of a large wheel that is made to turn using steam

• variable resistance: resistance which is able to be changed

• VAT: Value Added Tax; this is a tax imposed by the government on all consumable goods

• velocity: the rate of change of the position of an object, specifying the object's speed and direction

• voltage: the difference in potential energy per charge between two points in an electric circuit

• watt: unit of measurement for power; 1 watt is 1 joule per second

• weight: the gravitational force of attraction exerted on an object by the Earth (or Moon or any other planet)