Punjab PSEB Matric NSQF Power key terms

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

The electrical potential difference between two points that pushes charge through a circuit. Measured in volts; also called potential difference or electromotive force in source context.

The opposition a material offers to the flow of electric current, converting some energy to heat. Measured in ohms and depending on material, length, and cross-section.

The relationship stating that current through a conductor is directly proportional to voltage across it and inversely proportional to resistance, written V = I x R for constant temperature.

The SI unit of electric current, defined as the flow of one coulomb of charge per second through a conductor. Instrument used to measure it is an ammeter connected in series.

The SI unit of electric charge, equal to the charge carried by a current of one ampere flowing for one second. Used to quantify charge stored or transferred.

An instrument that measures electric current in amperes. It is connected in series with the circuit and has very low internal resistance so it does not disturb the current.

An instrument that measures potential difference in volts. It is connected in parallel across the component being tested and has very high internal resistance to avoid drawing current.

A combined measuring instrument that can check voltage, current, resistance and continuity. The digital type is common in trade work; correct range and function selection must be set before probing.

A check made with a meter to confirm that a conductor path is unbroken, usually indicated by a beep or near-zero resistance reading. The circuit must be de-energised first.

A material, usually a metal such as copper or aluminium, that allows electric current to flow easily because it has many free electrons. Used for wires and busbars.

A material such as rubber, PVC or porcelain that resists the flow of current and is used to separate or cover live conductors for safety.

A property of a material describing how strongly it opposes current for a given length and cross-section, quoted in ohm-metres. Copper has low resistivity; nichrome has high.

A circuit in which components are connected end to end so the same current passes through each, while the supply voltage divides across them. One break stops all current.

A circuit in which components are connected across the same two points so each receives the full supply voltage while current divides between branches. Common in domestic wiring.

The rate at which electrical energy is converted or transferred, measured in watts. In a resistive load it equals voltage multiplied by current, P = V x I.

The SI unit of power, equal to one joule of energy transferred per second. Appliance ratings are usually given in watts or kilowatts.

A unit of electrical energy equal to one kilowatt of power used for one hour. Electricity bills are calculated in these units, sometimes called one unit of electricity.

A device that records the electrical energy consumed by an installation over time, usually in kilowatt-hours. It forms the basis of billing and load monitoring.

Current that reverses direction periodically, typically 50 Hz in India. It can be stepped up or down by transformers, which makes it standard for generation and distribution.

Current that flows in one constant direction, supplied by batteries, solar cells and rectified adapters. Used in electronics and in some motor and welding applications.

The number of complete cycles of an alternating quantity per second, measured in hertz. Indian grid supply is standardised at 50 Hz.

A static device that changes AC voltage from one level to another by mutual induction between windings sharing a magnetic core. It works only on alternating current.

A circuit, often using diodes, that converts alternating current into direct current. Common in battery chargers, welding sets and electronic power supplies.

A two-terminal semiconductor device that allows current to flow mainly in one direction. Used in rectifiers, freewheeling paths and reverse-polarity protection.

A protective device containing a metal element that melts and opens the circuit when current exceeds its rating. It protects wiring from overload and short circuit.

A resettable automatic switch that trips on overload or short circuit to protect a circuit. It is rated by current and breaking capacity and can be switched back on after clearing the fault.

Connecting exposed metal parts of an installation to the ground through a low-resistance path so fault current flows safely away and protective devices trip.

An unintended low-resistance path between two points at different potential, causing very high current. It can damage equipment and start fires if not cleared quickly by a fuse or breaker.

A condition in which a circuit carries more current than its design rating for a period, often from too many appliances. It causes heating and is cleared by protective devices.

One or more insulated conductors bundled together, sometimes with a protective sheath, used to carry power between points. Size is chosen by current rating and voltage drop.

A standard number describing conductor cross-sectional area or diameter. Larger cross-section carries more current with less voltage drop and heating.

The reduction in voltage along a conductor caused by its resistance when current flows. Excessive drop causes dim lights and poor motor performance, so cable length matters.

The passage of current through the human body, causing burns, muscle contraction, or heart disruption. Severity depends on current magnitude, path, duration and skin condition.

A safety procedure in which the energy source is switched off, isolated, locked and tagged before work begins, preventing accidental re-energisation of equipment.

Wearable safety gear such as insulated gloves, safety shoes, helmet and eye protection that reduces injury risk. It supplements, but does not replace, safe work practices.

A transformer that steps medium distribution voltage down to utilisation level for consumers, typically mounted on a pole or plinth in a locality.

The ratio of useful output power to total input power, usually expressed as a percentage. Losses arise from copper heating, core magnetisation and mechanical friction.

A drawing using standard symbols to show how electrical components are connected, without regard to physical layout. Used for tracing circuits and fault finding.

A drawing that shows the physical arrangement and connection of wires and terminals in an installation or panel, helping with assembly and repair.