BTEB Electrician (EIM) Exam key terms

A safety procedure in which the power source is switched off, isolated, locked, and tagged so equipment cannot be re-energised while someone works on it.

Confirming with a tested voltage detector that a circuit or conductor carries no voltage before work begins or before earthing is applied.

Physically separating a circuit or equipment from every source of supply so that it cannot become live during maintenance or repair work.

The relationship stating that voltage equals current multiplied by resistance, written V = I × R, used to calculate any one value when the other two are known.

The relationship for electrical power, P = V × I, with related forms P = I²R and P = V²/R, used to size circuits and check loading.

The ratio of true power in watts to apparent power in volt-amperes in an AC circuit, equal to the cosine of the phase angle between voltage and current.

The property of a material that opposes the flow of electric current, measured in ohms and depending on material, length, and cross-sectional area.

A material constant showing how strongly a substance resists current flow per unit length and area, used to calculate conductor resistance from its dimensions.

The loss of voltage along a conductor caused by its resistance when current flows, which must be kept within permitted limits for proper equipment operation.

The property of a coil or circuit that opposes changes in current by producing a counter electromotive force, measured in henries.

The ability of two separated conductors to store electric charge when a voltage is applied, measured in farads and used in power-factor correction.

An AC supply of three voltages equal in magnitude and 120 electrical degrees apart, used for motors and heavy loads because it gives smoother power delivery.

Two ways of connecting three-phase windings: star joins one end of each winding at a neutral point, while delta connects them end to end in a loop.

The maximum current a cable can carry continuously without its insulation exceeding its permitted temperature, given installation method and ambient conditions.

A multiplier below one applied to a cable's tabulated current rating to allow for grouping, high ambient temperature, or thermal insulation around the cable.

An allowance recognising that not all connected loads operate at the same time, used to size supply cables and protective devices realistically.

The greatest load a consumer's installation is expected to draw at any one time, calculated after applying diversity to the total connected load.

Connecting exposed conductive parts and the supply neutral point to the general mass of earth so fault current flows and protection operates quickly.

The total resistance of the path taken by fault current through the earth and back to the supply, which must be low enough to trip protection fast.

A protective device that trips when it detects a small imbalance between line and neutral current, indicating leakage to earth or through a person.

A switch that automatically opens a circuit on overload or short circuit and can be reset, available in miniature, moulded-case, and air types.

A protective device containing a element that melts and breaks the circuit when current exceeds its rating for a set time, then must be replaced.

The maximum fault current a protective device can safely interrupt without damage to itself or danger to the surrounding installation.

Coordination of protective devices so that the device nearest a fault operates first, leaving the rest of the installation energised.

An electromagnetically operated switch used to control power circuits repeatedly, holding its contacts closed while its coil stays energised.

A protective device that senses sustained excess current in a motor circuit and opens the control circuit before the motor winding overheats.

A control arrangement that prevents one action unless another condition is met, such as stopping a forward contactor before reverse can energise.

A motor starter that connects the motor directly to the full supply voltage, giving high starting torque but drawing a large starting current.

A starter that runs the motor windings in star during acceleration to reduce starting current, then changes to delta for normal running.

A switch operated by the movement of a machine part or door, used to stop travel, reverse direction, or confirm a safe position.

A static device with two windings on a common magnetic core that changes AC voltage level while transferring power by electromagnetic induction.

The ratio of primary to secondary winding turns, which sets the ratio between primary and secondary voltages in a transformer.

A test using a high-voltage DC instrument to measure how well insulation resists leakage, expressed in megohms and compared with a minimum value.

A check confirming that a conductor or protective path is unbroken and has low resistance, usually made with a low-voltage ohmmeter or buzzer.

A verification that line, neutral, and switch connections are in the correct positions so switches control the line conductor, not the neutral.

A wiring arrangement using two two-way switches so a lamp can be controlled from either of two positions, such as both ends of a stairway.

A method adding a four-terminal intermediate switch into a two-way circuit so the same lamp can be controlled from three or more positions.

A wiring method where circuit cables run from ceiling rose to ceiling rose and switches are fed by separate drops, avoiding joints in the main run.

A tube of metal or plastic that carries and mechanically protects insulated conductors, either buried in walls or mounted on the surface.

A rectangular enclosure with a removable lid used to carry and protect cables or conductors, often surface-mounted where wiring may be altered.

An open metal or plastic support system carrying cables in industrial and commercial installations, allowing easy inspection and heat dissipation.

A precision measuring instrument with a calibrated screw used to measure the diameter of wire or the thickness of sheet metal accurately.

A measuring tool with a sliding jaw and a vernier scale used to read internal, external, and depth dimensions to a fraction of a millimetre.

A fitting that secures a cable where it enters an enclosure and provides strain relief, sealing, and often an earth connection to armour.

A drawing showing the electrical connections and function of a circuit without regard to the physical position of the components.

A drawing showing components in roughly their physical positions with the connections between them, used for installation and fault finding.

A table listing each circuit, its connected load, protective device rating, and cable size, used for design and inspection documentation.

A document listing each cable run with its type, size, route, and end points, helping installation, material take-off, and later maintenance.

A circuit or device, often using diodes, that converts alternating current into direct current for supplies, chargers, and drives.

A device that converts direct current into alternating current, used in variable-speed drives, backup supplies, and solar installations.

A two-terminal semiconductor that conducts current mainly in one direction, used for rectification, protection, and freewheeling in control circuits.

A three-terminal semiconductor used as an amplifier or an electronic switch, forming the basis of sensors, relays drivers, and control logic.

An electronic unit that varies the frequency and voltage fed to a motor, allowing controlled speed and reduced starting current.

An industrial computer that runs a stored program to read inputs and switch outputs, replacing relay logic in machine and process control.

Items worn to reduce injury risk, such as insulating gloves, safety footwear, eye protection, and arc-rated clothing, selected for the task.

A structured review identifying hazards, judging how likely and severe harm could be, and recording controls before work starts.

A written description of how a job will be carried out safely, listing sequence, tools, controls, and responsible persons.