Maharashtra SSC Electrical Appliances (MSBSHSE) key terms

The rate at which electric charge flows through a conductor, measured in amperes. One ampere equals one coulomb of charge passing a point each second.

The work needed to move a unit positive charge between two points in a circuit, measured in volts. It is the electrical pressure that drives current through a conductor.

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

A relationship stating that current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance, written as V equals I times R, at constant temperature.

The rate at which electrical energy is converted into another form, measured in watts. For a resistive load it equals voltage multiplied by current.

The total work done by an electric circuit over time, measured in joules or, for billing, in kilowatt-hours. One kilowatt-hour equals the energy used by a one-kilowatt load running for one hour.

A property of a material expressing how strongly it resists current flow, quoted in ohm-metres. Copper has low resistivity, so it is preferred for conductors; nichrome has high resistivity and suits heating elements.

A material that allows electric current to pass easily because it contains many free electrons. Copper, aluminium and silver are common examples used in wiring and appliance leads.

A material that strongly opposes current flow and is used to separate or cover live parts. Rubber, PVC, porcelain and dry air are typical insulating materials in appliances and wiring.

The resistance measured between a live conductor and earth, or between two insulated conductors, indicating the health of insulation. A low reading usually signals moisture, damage or contamination.

A screwdriver whose shaft is covered with insulating material up to the tip, protecting the user from shock when working near live parts. Its insulation must be undamaged before use.

Wearable safety gear such as insulated gloves, safety shoes, goggles and helmets that reduces injury risk during electrical work. It supplements, but never replaces, safe isolation and correct procedure.

The process of disconnecting an appliance or circuit from every source of supply and securing it against reconnection before work begins. Isolation is verified by testing for the absence of voltage.

A safety procedure in which the isolating switch is locked in the off position and a warning tag is attached, so that supply cannot be restored while someone is working on the circuit.

The three conductors of a domestic supply: phase carries live voltage, neutral provides the return path, and earth is a safety conductor connected to the installation's earthing system.

A switch with one common terminal and two way terminals, allowing a lamp to be controlled from two positions when paired with another two-way switch in a staircase circuit.

A fixed accessory that supplies portable appliances through a plug. In India, domestic sockets are commonly rated 6 A or 16 A and must be wired with the correct polarity and earthing.

A resettable protective device that trips automatically on overload or short circuit and can be switched back on after the fault is removed. Its rating is chosen to protect the cable it supplies.

A protective device containing a metal element that melts and breaks the circuit when current exceeds its rating. It must be replaced after operation and must never be rewired with thicker wire.

A device that detects small currents flowing to earth, as happens when a person touches a live part or insulation fails, and disconnects the supply quickly to prevent fatal shock.

Deliberate connection of exposed metal parts of an installation to the general mass of earth, so that fault current flows safely away and protective devices operate promptly.

An unintended low-resistance path between phase and neutral or phase and earth, causing a very large current that blows a fuse or trips a breaker almost instantly.

A condition in which a circuit or appliance carries more current than its design allows for a sustained period, causing overheating. It is less severe than a short circuit but still damaging.

A resistor, usually made of nichrome wire inside a ceramic or metal sheath, that converts electric energy into heat. Its resistance and length set the power it delivers.

A temperature-operated switch that opens and closes the heater circuit to hold an appliance near a set temperature. Bimetallic strip types bend with heat to make or break contact.

A one-shot safety device that melts at a fixed temperature and permanently cuts off the heater if the thermostat fails, preventing fire in appliances such as irons and heaters.

A small series-wound motor that runs on either AC or DC and reaches high speed, used in mixers, vacuum cleaners and drills. Its brushes and commutator need periodic inspection.

A single-phase induction motor in which a capacitor in the starting winding creates phase shift and high starting torque. The capacitor or centrifugal switch is a common cause of failure to start.

A speed-operated switch on the motor shaft that disconnects the starting winding once the rotor reaches about three-quarters speed. Sticking contacts leave the motor humming without rotating.

A simple instrument, often a battery lamp or buzzer, used to check whether a path exists between two points. It must only be used on dead circuits.

An instrument that applies a high test voltage to measure insulation resistance in megohms. Readings are taken between live parts and earth and between conductors.

A general-purpose test instrument that measures voltage, current and resistance, and often continuity. Correct range and function selection are essential to avoid damage or danger.

The ratio of true power in watts to apparent power in volt-amperes in an AC circuit. A low value means more current is drawn for the same useful work.

A measure comparing useful output of an appliance with the electrical energy it consumes, such as cooling output per watt for air conditioners. A higher ratio means lower running cost.

A standardised label on appliances in India showing energy efficiency on a scale of one to five stars, with higher stars indicating lower electricity consumption for the same performance.

Electricity consumed by appliances while switched off but still connected, for remote control or display circuits. Unplugging or switching off at the socket eliminates this waste.