Odisha CHSE +2 Vocational EDA (Electrical Domestic Appliances) key terms

The work done per unit charge in moving charge between two points in a circuit, measured in volts with a voltmeter connected in parallel across the points.

The statement that current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance, at constant temperature.

The opposition a material offers to the flow of electric current, measured in ohms and depending on material, length, cross-section and temperature.

A property of a material expressing the resistance of a unit length with unit cross-sectional area, quoted in ohm-metres and used to compare conductors and insulators.

The cosine of the phase angle between voltage and current in an alternating circuit, showing what fraction of apparent power does useful work.

A portable test instrument combining voltmeter, ammeter and ohmmeter functions, used for routine measurement and continuity checking of domestic appliance circuits.

An insulation resistance tester that applies a high direct voltage, typically 500 V, to measure leakage through insulation in megohms before wiring is energised.

A material such as copper or aluminium that offers low resistance to current flow and is used to carry supply to appliances.

A material such as PVC, rubber or porcelain that strongly resists current flow and is used to separate live parts from people and earthed metalwork.

The resistance measured between a live conductor and earth or between windings, indicating whether insulating material is sound or degraded.

Deliberate connection of exposed metal parts of an installation to the general mass of earth so fault current trips protection instead of energising the casing.

The verified low-resistance path from an appliance metal body back to the earth electrode, tested with an ohmmeter to confirm protective bonding is intact.

A resettable automatic switch that opens a circuit on overload or short circuit, rated by current and breaking capacity, and used in domestic distribution boards.

A protective device that trips when current leaking to earth exceeds a set sensitivity, commonly 30 milliamperes, protecting people from electric shock.

A deliberately weak link of wire or strip that melts and breaks the circuit when current exceeds its rating, giving one-shot overload and short-circuit protection.

An accidental low-resistance path between live conductors or between live and neutral, causing very high current that must be cleared instantly by protective devices.

A sustained current above the rated value of a circuit or appliance that raises temperature without being a full short circuit, such as a jammed mixer motor.

A wiring accessory with a common terminal and two strappers that lets one lamp be controlled from either of two positions, as on a staircase.

A lighting arrangement using two two-way switches at the ends of a stair so the lamp can be switched on or off from either landing.

The conductor that carries supply potential to the appliance, coloured by convention in the installation and always treated as dangerous until isolated and proved dead.

The return conductor of a supply system, normally near earth potential, which completes the circuit back to the source transformer.

A check made with an ohmmeter or buzzer on a de-energised circuit to confirm an expected path exists, such as through a switch contact or heater element.

A temperature-sensitive switch, often bimetallic, that opens the heater circuit when a preset temperature is exceeded and resets or must be replaced afterwards.

An adjustable temperature-operated switch that opens and closes the heating circuit to hold an appliance such as an iron, geyser or refrigerator at a set temperature.

A resistance wire, usually nichrome, wound on a former and enclosed in a sheath, which converts electrical energy into heat in appliances like heaters and irons.

A nickel-chromium alloy with high resistivity and good oxidation resistance at high temperature, widely used for appliance heating elements.

An alternating-current motor in which a rotating magnetic field induces current in a rotor, commonly the capacitor-start type used in fans and washing machines.

A component that stores charge and, in single-phase motors, creates a phase shift to give starting torque; a failed capacitor stops the fan or motor from turning.

A sliding contact that carries current to the rotating commutator of a universal motor, wearing down over time and needing inspection or replacement.

A series-wound motor that runs on either direct or alternating current at high speed, used in mixers, grinders and vacuum cleaners.

The segmented rotating switch on a direct-current or universal motor armature that reverses winding current at the right moment to keep the rotor turning.

A fluid that absorbs heat by evaporating at low pressure in the evaporator and releases it by condensing at high pressure in the condenser of a refrigeration circuit.

The pump in a refrigeration system that raises refrigerant pressure and temperature, driving the vapour around the circuit from evaporator to condenser.

A narrow-bore tube used as an expansion device, dropping refrigerant pressure between condenser and evaporator and regulating flow in small domestic refrigerators.

The product of root-mean-square voltage and current in an alternating circuit, measured in volt-amperes, combining useful power and reactive power.

A lighting fitting using semiconductor junctions to produce light efficiently at low power, with a driver circuit that converts mains supply to the required direct current.

A choke or electronic control unit in a discharge lamp circuit that limits current and, in fluorescent fittings, provides the starting voltage surge.

The light output of a lamp divided by the electrical power it consumes, expressed in lumens per watt and used to compare lamp efficiency.

The process of adding up connected appliance loads and applying diversity to decide cable size, circuit protection rating and distribution board capacity for a dwelling.