Alternator – electromechanical device that turns mechanical energy into alternating current (AC) electricity.
Alternating current (AC) – current repeatedly changes direction of flow.
Ammeter – device used to measure current flow.
Amp (A) – unit of electric current.
Armature – generally relates to a movable piece of ferromagnetic metal placed between poles of a magnet. For example, the rotating core of an electric motor or alternator, or the moving arm of a relay.
Atom – the smallest part of an element that can exist.
Battery – a collection of cells connected together to deliver direct current (DC). Different methods of connection determine the voltage and the size of cells determines available current.
Capacitance – the ability of a device to store an electrical charge.
Capacitor – a device capable of storing an electrical charge.
Cell – a device capable of releasing stored energy in the form of electricity, as a result of a chemical reaction.
Circuit – the configuration of an electrical source, conductors and devices, in order to be capable of carrying current.
Conductance – the opposite of resistance, relates to the ease with which electricity will pass through material.
Conductor – material that electricity will flow through with little resistance.
Consultation – the process of meeting for deliberation, discussion or decision.
Coulomb – practical unit of an electrical charge. The quantity of electric charge transferred each second by a current of one ampere.
Current (I) – the movement or flow of electrons along a conductor. The symbol for current is I and the unit of measure is amps (A).
Diameter – the distance from one side of a circle to the other; the symbol is a circle with a line through it (ø).
Diode – a semi-conductor device that allows current flow in one direction only.
Direct current (DC) – current that flows in one direction only.
Efficiency – the efficiency of an electrical machine can be determined by comparing the input power against the output power.
Electrode – a conductor where current passes from a solid into a liquid, into a gas, or into a vacuum, or vice versa.
Electrolysis – chemical change to material as a result of the passage of an electric current through an electrolyte.
Electrolyte – a conducting substance or medium, eg acid, base or salt, in which the flow of current is accompanied by the movement of matter in the form of ions.
Electromagnet – a magnet that is created by passing electrical current through a coil wound around an iron core.
Electromotive force (EMF) – voltage between the terminals of a cell or generator in the open circuit condition.
Electron – negatively charged particle of an atom.
Farad (F) – derived unit of measure for capacity that exists between two plates of a capacitor if the transfer of one coulomb from one plate to the other creates a potential difference of one volt.
Field – a region where magnetic lines of force can be detected from a magnet or electrical circuit.
Free electron – an electron that is not bound to any particular atom and can therefore move from atom to atom in a conductor.
Frequency – the number of times per second that something changes. Relates to alternating current in particular and is measured in hertz (Hz).
Galvanometer – device for measuring or detecting small amounts of current.
Galvanised – protective coating on iron to prevent rust, achieved by the use of a galvanic current or zinc coating.
Henry (H) – unit of measure of inductance. If the rate of change of current in a circuit is one ampere per second, and the resulting electromotive force is one volt, then the inductance of the circuit is one henry.
Hertz (Hz) – unit of measure of frequency, one hertz (Hz) equals once per second.
Insulator – material that is highly resistive to conducting electricity.
Ion – atom or molecule that has become electrically charged by either gaining or losing electrons.
Isometric – (isometric projection) a three-dimensional drawing with horizontal edges of the object drawn usually at a 30° angle and all verticals projected perpendicularly from a horizontal base; all lines are drawn to scale.
Impedance – the opposition that is present in a circuit to the passage of alternating current. The symbol for impedance is Z; it is measured in ohms.
Inductance – relates to the characteristic of a circuit to have a voltage induced into it by current variation within the circuit itself (self-inductance) or from a nearby circuit (mutual-inductance). The henry (H) is the unit of measure for inductance.
Inverter – an electrical device that converts direct current (DC) into alternating current (AC).
Joule (J) – the unit of work or energy. It is equal to one watt for one second.
Kelvin (K) – International System (SI) unit of temperature.
Legislation – relates to law and includes Acts, Ordinances, Regulations and other forms of delegated legislation such as rules and bylaws.
Load – a device, appliance or component in an electrical circuit that performs work and therefore consumes energy, eg lamp, motor, etc.
Magnetic – refers to the invisible magnetic field that surrounds a magnet or electromagnet.
Metre (m) – International System (SI) unit of length.
Multimeter – meter that is capable of measuring a range of different electrical values.
Neutron – neutral (uncharged) particle of an atom found in all atoms except hydrogen.
Newton (N) – International System (SI) unit of force.
Ohm (Ω) – derived unit for measurement of resistance. If a device dissipates one watt of power with one ampere of current flowing through, it has a resistance of one ohm (R = P/I2).
Ohmmeter – a device used for measuring resistance in ohms.
Open circuit – an electrical circuit that is not complete; there is a break in the circuit therefore no current is flowing. An open circuit can be from a switch being open in the circuit or a fault in the circuit.
Orthogonal – an orthogonal projection; relates to or involves right angles or perpendiculars.
Parallel – in the same direction. A parallel circuit is where a number of electrical loads are arranged in relation to the one voltage supply to have individual current flow paths.
Pascal (Pa) – International System (SI) unit of pressure.
Perpendicularly – straight up and down; vertical or upright.
Pole – (1) Either terminal of a battery or cell. (2) Either end of a magnet.
Potential difference – the work needed to transfer one unit of charge between two points, measured in volts (V).
Potentiometer – a type of variable resistor used for voltage adjustment.
Power – the rate at which energy is converted from one form to another. The unit of measurement of power is the watt (W).
Proton – the positively charged particle of an atom.
Radius (r) – the distance from the centre to the circumference (outside line) of a circle.
Rehabilitation – to restore to a condition of good health in order to be able to get back to work.
Relay – switch device operated by electromagnetism.
Residual – something that is left over or remaining, eg residual current.
Resistance (R) – the opposition to current flow. In an electrical circuit everything has some resistance, including conductors. The symbol for resistance is R and it is measured in ohms (Ω).
Resistor – device designed to have a specific amount of resistance, specified in ohms (Ω).
Rheostat – a type of variable resistor used to vary current flow.
Semiconductor – material with electrical conducting properties intermediate between that of metal and insulators.
Series – one after the other. A series circuit is where one load is placed after another in the same circuit , so there is only one path for current flow.
Short circuit – a fault condition where a low resistance connection has happened across an electrical circuit resulting in high current flow. Often referred to as a 'short'.
Shunt – a circuit component connected in parallel with another.
Static – stationary or not moving. Static electricity relates to a build up of electrical charge without any current flow.
Thermal – relates to using, caused by or producing heat.
Thermistor – electrical device that reduces resistance as temperature increases.
Thermocouple – device having junction between two dissimilar metals; when heated an EMF is produced.
Thermopile – several thermocouples joined in series to produce a combined EMF.
Three phase – source of electrical power from three separate alternating voltages that are out of phase with each other by one-third.
Transformer – a device that uses coils to convert AC voltage and current from one value to a different value voltage and current.
Valence shell – the outermost orbit path for electrons in an atom is known as the valence shell or conduction band.
Volt (V) – derived unit of measure for the potential difference existing between two points on a conductor.
Voltmeter – device used for measuring volts.
Voltage drop – reduction in voltage in a part of a circuit between the power source and the load. Caused by resistance in a DC circuit or impedance in an AC circuit.
Watt – derived unit of measure for power used when energy is expended at the rate of one joule per second.