HSC Electrotechnology (VET) key terms

A complete closed path through which electric current can flow, made up of a source, conductors, and a load. If the path is broken anywhere, current stops flowing.

The electrical pressure or potential difference that pushes charge around a circuit. Measured in volts (V) with a voltmeter connected in parallel across the points being compared.

The rate at which electric charge flows past a point in a circuit, measured in amperes (A). An ammeter is connected in series so the current passes through it.

The opposition a material offers to current flow, measured in ohms. It depends on the material, its length, its cross-sectional area, and its temperature.

The relationship stating that voltage equals current multiplied by resistance (V = I x R) in a resistive circuit. Knowing any two values lets you calculate the third.

The rate at which electrical energy is converted into another form, measured in watts. In a circuit it equals voltage multiplied by current (P = V x I).

The total amount of work electricity performs over time, measured in joules or kilowatt-hours. It equals power multiplied by the time the load operates.

A practical unit of electrical energy equal to 1000 watts used continuously for one hour. Electricity retailers bill customers using this unit.

A circuit where components are connected end to end so the same current flows through each one. Total resistance is the sum of the individual resistances, and supply voltage divides across loads.

A circuit where components are connected across the same two points, so each receives the full supply voltage. Total current is the sum of the branch currents.

A material, usually a metal such as copper or aluminium, that allows electric charge to flow easily because it contains many free electrons.

A material that resists the flow of electric current, such as rubber, plastic, or glass. Insulation around conductors protects people from electric shock.

Current that flows in one constant direction, such as from a battery or a solar panel through a regulator. Often abbreviated DC.

Current that regularly reverses direction, as supplied by the mains grid. In Australia it reverses 50 times per second, giving a frequency of 50 hertz.

The number of complete cycles of an alternating waveform that occur each second, measured in hertz (Hz). Australian mains supply operates at 50 Hz.

An instrument used to measure electric current in amperes. It is connected in series with the circuit so that the current being measured passes through it.

An instrument used to measure potential difference in volts. It is connected in parallel across the component or points whose voltage difference is being measured.

A versatile test instrument that can measure voltage, current, resistance, and sometimes continuity. The correct function and range must be selected before connecting it to a circuit.

A check confirming that a conductive path exists between two points with very low resistance. It is performed with the circuit de-energised, often using the multimeter's buzzer setting.

A circuit in which the conductive path is broken, so no current can flow. Common causes include a blown fuse, a loose connection, or an open switch.

An unintended low-resistance path that bypasses the load, causing excessive current to flow. It can damage equipment and start fires, so protective devices must operate quickly.

A protective device containing a metal element that melts and breaks the circuit when current exceeds its rating. Once it operates, it must be replaced.

A resettable protective switch that automatically opens a circuit when current exceeds its rating. It can be manually reset after the fault is corrected.

A safety switch that detects small differences between active and neutral current, indicating leakage to earth, and rapidly disconnects the supply to prevent electric shock.

Connecting exposed metal parts and the electrical system to the ground so fault current has a safe path. It helps protective devices operate and reduces shock risk.

The conductor that carries current to the load from the supply. In single-phase wiring it is often coloured brown in fixed wiring and identified by switching.

The return path for current in a normal operating circuit, connected to the supply's neutral point. It is normally near earth potential but is still a current-carrying conductor.

A protective conductor that connects exposed metalwork to the earthing system. It normally carries no current but provides a low-resistance fault path.

One or more insulated conductors bundled together, often with an outer sheath, used to distribute electrical energy between points in an installation.

A tube or channel, usually plastic or metal, that routes and protects electrical cables and wiring against mechanical damage, moisture, and interference.

A rigid support system, usually metal, used to carry and support multiple cables in industrial and commercial installations while keeping them organised and ventilated.

The resistance measured between a conductor and earth, or between conductors, to check that insulation is sound. Low readings indicate damaged or deteriorated insulation.

A test instrument that applies a high DC voltage to measure very high resistance values, commonly used for insulation resistance testing of cables and motors.

A device with two or more coils that transfers electrical energy between circuits by electromagnetic induction, stepping voltage up or down with little loss.

An electrical component or circuit, typically using diodes, that converts alternating current into direct current for equipment such as chargers and power supplies.

A semiconductor component that allows current to flow easily in one direction but blocks it in the reverse direction. It is used for rectification and protection.

A material such as silicon whose conductivity lies between that of a conductor and an insulator, and which can be controlled to make diodes and transistors.

The physiological effect of current passing through the human body, which can cause burns, muscle contraction, heart rhythm disturbance, or death depending on current and duration.

The process of disconnecting and locking off all supply sources so equipment is safe to work on. Isolation must be verified before touching conductors.

A safety procedure in which energy sources are switched off, locked, and tagged to prevent accidental re-energisation while maintenance or repair work is carried out.