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.