Punjab PSEB Matric NSQF Electronics key terms

The steady flow of electric charge through a conductor, measured in amperes with an ammeter connected in series. One ampere equals one coulomb of charge passing a point each second.

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

The opposition a material offers to current flow, measured in ohms. It depends on material, length, cross-sectional area and temperature, and converts electrical energy into heat.

For a metallic conductor at constant temperature, current is directly proportional to applied voltage and inversely proportional to resistance, written V = IR. It underpins nearly all basic circuit calculations.

A passive component made to provide a definite resistance in a circuit. Fixed types use colour bands; variable types such as potentiometers allow adjustment of voltage or current.

A standard banding system printed on resistors to show value and tolerance. Each colour stands for a digit; the third band gives the multiplier and the last band the tolerance percentage.

A connection in which components form a single path so the same current passes through each. Total resistance is the sum of individual resistances and the supply voltage divides across them.

A connection in which components are joined across the same two nodes, so each receives the full supply voltage while current divides between branches. Total resistance is always less than the smallest branch.

Two rules for analysing networks: the current law states that currents entering a junction equal those leaving, and the voltage law states that voltages around any closed loop sum to zero.

A component that stores charge in the electric field between two conducting plates separated by a dielectric. Capacitance is measured in farads and blocks steady direct current while passing alternating current.

A coil that stores energy in a magnetic field when current flows through it. Its inductance, measured in henries, opposes changes in current and depends on turns, core and geometry.

The total opposition, including resistance and reactance, that a circuit presents to alternating current. It is measured in ohms and combines the two as a vector sum.

The frequency-dependent opposition offered by a capacitor or inductor to alternating current, measured in ohms. Capacitive reactance falls as frequency rises, while inductive reactance rises with frequency.

The condition in an LC circuit where inductive and capacitive reactances are equal and cancel, leaving only resistance. It occurs at a frequency calculated from inductance and capacitance values.

A circuit that converts alternating current into direct current using diodes. Half-wave types use one diode; full-wave and bridge types use two or four to use both halves of the cycle.

A two-terminal semiconductor device that conducts easily in one direction and blocks the other. Silicon types need about 0.7 volts forward bias to conduct appreciable current.

A specially doped diode designed to operate safely in reverse breakdown at a precise voltage. It is used as a shunt regulator and voltage reference in power supplies.

A three-terminal semiconductor device in which a small base current controls a larger collector current, giving amplification or switching action. Bipolar and field-effect types are the main families.

Setting the steady direct voltages and currents at a transistor's terminals so it works in the desired region of its characteristic curves. Proper bias prevents distortion in amplifiers.

A circuit that increases the amplitude of a signal using the energy of a supply, without changing its waveform shape. Gain is usually expressed in decibels.

A high-gain integrated amplifier with inverting and non-inverting inputs, used with feedback to perform addition, comparison and filtering. Ideal types have infinite gain and input impedance.

Returning a fraction of an amplifier's output to its input in opposite phase. It reduces gain but improves stability, bandwidth and linearity, and lowers distortion.

A circuit that generates a continuous periodic waveform from a direct supply, using positive feedback and a frequency-selective network. Common types include RC phase-shift and crystal oscillators.

A basic digital building block that gives an output determined by fixed rules from its inputs. AND, OR and NOT are fundamental; NAND and NOR are called universal gates.

A table listing every possible combination of inputs to a logic circuit alongside the resulting output. It is the standard way to define and verify digital behaviour.

A bistable digital storage element that holds one bit until clocked or triggered to change state. It forms the basis of registers, counters and memory.

A pair of magnetically coupled coils that changes alternating voltage levels. A step-down type has fewer secondary turns; rating is given in volt-amperes, not watts.

A handheld test instrument combining voltmeter, ammeter and ohmmeter functions, often with continuity and diode tests. Correct range and probe placement prevent damage and wrong readings.

A test instrument that displays signal voltage against time on a screen, allowing measurement of amplitude, period and waveform shape. Probes must be compensated and correctly grounded.

Joining metal parts with a low-melting filler alloy to make an electrical and mechanical bond. Good joints are shiny and concave; a cold joint looks dull and grainy.

A chemical agent applied during soldering to remove oxide films and help the solder wet the joint. Rosin is common in electronics; residues may need cleaning afterwards.

A faulty solder connection where the alloy has not properly wetted the surfaces, giving high resistance and intermittent operation. It usually appears dull, lumpy or cracked.

An insulating board with copper tracks that connect and support components. Assembly involves placing parts, soldering, trimming leads and inspecting for bridges or missing joints.

A spring-loaded suction tool used to remove molten solder from a joint so a component can be taken out. It is used together with a hot iron and sometimes solder wick.

A check made with a meter to confirm a very low-resistance path exists, often signalled by a beep. The circuit must be unpowered and isolated before testing.

The resistance measured between a conductor and earth or between separate conductors, indicating how well insulation prevents leakage. It is tested with an insulation tester at high voltage.

Connecting exposed metalwork of equipment to the general mass of earth through a low-resistance path. It makes protective devices operate and limits touch voltage during a fault.

A resettable protective device that trips on overload or short circuit using thermal and magnetic elements. It is rated by current and breaking capacity and replaces rewirable fuses.

A component with small pads that is soldered flat onto the board surface rather than through holes. Hand assembly needs fine tips, tweezers and careful heat control.