Barbados Wireman Licence Exam key terms

The fixed relationship in a circuit stating that current equals voltage divided by resistance, so a higher voltage pushes more current and a higher resistance allows less.

The total opposition a circuit offers to alternating current, combining resistance with reactance so that current and voltage may not rise and fall together.

The ratio of real power doing useful work to the total apparent power supplied, expressed as a decimal or percentage and reduced by inductive or capacitive loads.

The reduction in voltage along a conductor caused by its resistance and the current flowing through it, calculated from conductor size, length and load current.

The maximum continuous current a conductor can carry under stated installation conditions without its insulation exceeding its rated temperature limit.

A multiplier applied to a cable's tabulated current rating to account for conditions such as grouping, high ambient temperature or thermal insulation that reduce its ability to shed heat.

A multiplier used when the surrounding air or ground is hotter or colder than the reference temperature assumed in the current-carrying table for that cable type.

The assumption that not all connected loads operate at full demand simultaneously, allowing the maximum demand of an installation to be assessed as less than the total connected load.

The greatest load, usually averaged over a set period, that an installation or circuit is expected to draw, used to size service conductors and protective devices.

Connecting exposed metalwork and the installation's protective conductors to the general mass of earth so that fault current has a low-impedance path back to the supply source.

Permanently joining metal parts together, or to the earthing system, so they remain at substantially the same potential and cannot develop a dangerous voltage between them.

Connecting all simultaneously accessible metalwork, including incoming metallic services, so that no hazardous potential difference can appear between them during a fault.

The common bar or block in an installation to which the earthing conductor, circuit protective conductors and main bonding conductors are all connected.

A conductor provided specifically to carry fault current or to connect exposed metalwork to earth, commonly called the earth wire in a circuit cable.

The protective conductor connecting exposed conductive parts of a final circuit back to the main earthing terminal, ensuring fault current trips the protective device quickly.

The resistance between an earth electrode and the surrounding ground, which must be low enough for protective devices to operate and for touch voltages to stay safe.

The total impedance of the path taken by fault current from the source, through the live conductor, the fault, the protective conductor and back to the source.

The maximum permitted interval within which a protective device must automatically cut off supply after a fault, set by regulation according to circuit type and voltage.

A protective device that continuously compares live and neutral currents and trips when their difference, representing leakage to earth, exceeds its rated residual operating current.

A manually resettable automatic switch that opens on overload or short circuit, rated by its nominal current and its breaking capacity.

The current a fuse is designed to carry continuously without melting, together with its fusing factor that determines how quickly it operates at higher currents.

The maximum prospective fault current a protective device can safely interrupt without damage or dangerous arcing, sometimes called short-circuit capacity.

The current that would flow at a given point if a short circuit of negligible impedance occurred there, calculated from supply voltage and circuit impedance.

A test applying a steady direct voltage between conductors and earth to confirm insulation is sound, with results recorded in megohms and compared against a minimum acceptable value.

A low-resistance check confirming that protective conductors, bonding conductors and ring final circuit conductors form an unbroken, properly connected path.

A verification that line, neutral and protective conductors are connected to the correct terminals throughout the installation, so switches and fuses are in the live conductor.

An instrument check confirming a residual current device trips within its rated residual current and permitted time, including verification of its test button operation.

A socket-outlet circuit whose conductors form a closed loop from the consumer unit, allowing each leg to share the load and requiring continuity verification of all conductors.

The enclosure at the origin of a domestic or small commercial installation housing the main switch, protective devices and earthing and bonding terminals for final circuits.

The point where the supply authority's conductors enter the premises, including the meter position, main switch and the origin of the installation's earthing arrangements.

The unit of apparent power in an alternating current circuit, equal to the product of root-mean-square voltage and current without regard to phase difference.

A fitting that secures a cable where it enters an enclosure and, where required, provides strain relief and electrical continuity between cable armour and the enclosure.

A two-digit code stating how well an enclosure resists entry of solid objects and water, used to select equipment suitable for the environment where it is installed.

A support system of perforated or ladder-section metal on which cables are laid, requiring correct spacing, fixing and earthing of the tray itself.

A written description of how a particular job will be carried out safely, listing the sequence of work, the hazards identified and the controls to be applied.

A careful examination of what in the work could cause harm, evaluating how likely and how serious that harm is and deciding what precautions are reasonably practicable.

The procedure of switching off, proving dead, and securing the supply with locks and warning tags so that equipment cannot be re-energised while work proceeds.

Testing an isolated circuit with a proven voltage indicator at the point of work to confirm no dangerous voltage is present before touching conductors.

A formal written authorisation issued for high-risk work, recording the isolation applied, the precautions taken and the person authorised to carry out the task.

The formal document issued on completion of new work or a major alteration, declaring the design, construction, inspection and testing comply with the wiring regulations.

A shorter certificate used for small additions or alterations that do not include a new circuit, covering the work done and the tests carried out on it.

A report produced after inspecting and testing an existing installation at planned intervals, recording its condition, defects found and any recommended remedial action.

The accompanying record listing each circuit's protective device, conductor sizes, and measured insulation resistance, continuity, loop impedance and RCD trip times.