WBBSE Madhyamik Electronics (Vocational) key terms

The rule that the current through a conductor equals the voltage across it divided by its resistance (I = V/R), valid at constant temperature for linear materials.

The electrical potential difference between two points, measured in volts, that drives charge through a circuit. It is the energy transferred per unit charge.

The rate at which electric charge flows past a point in a circuit, measured in amperes, where one ampere equals one coulomb per second.

The opposition a material offers to the flow of electric current, measured in ohms. It converts electrical energy into heat and depends on material, length and cross-section.

The rate at which electrical energy is used or delivered, measured in watts. It equals voltage multiplied by current (P = VI) and also equals I squared R.

A connection where components form a single path, so the same current flows through each and the total resistance is the sum of the individual resistances.

A connection where components share the same two nodes, so the voltage across each is equal and the total resistance is less than the smallest branch resistance.

A standard scheme of coloured bands printed on a resistor that encodes its resistance value and tolerance, read from the band nearest one end.

A passive two-terminal component made of carbon, metal film or wire that limits current and sets voltage levels in a circuit, rated by resistance and wattage.

A three-terminal variable resistor whose wiper taps a adjustable fraction of the applied voltage, commonly used as a volume or sensitivity control.

A passive component of two conducting plates separated by a dielectric that stores charge and energy in an electric field, blocking direct current while passing alternating current.

The ability of a capacitor to store charge per unit voltage, measured in farads. It depends on plate area, plate spacing and the dielectric material between the plates.

A polarised capacitor with an oxide dielectric and a liquid or gel electrolyte, offering large capacitance in a small body; it must be connected with correct polarity.

A coil of wire that stores energy in a magnetic field, opposes changes in current and is measured in henries; it is the basis of transformers and chokes.

The permitted deviation of a component's actual value from its marked value, usually expressed as a percentage such as plus or minus five percent for a gold band.

The boundary formed where p-type and n-type semiconductor material meet, which conducts in one direction and creates a depletion region with a barrier potential.

A two-terminal semiconductor device with a single PN junction that conducts current easily in forward bias and blocks it in reverse bias, used for rectification and protection.

The narrow zone around a PN junction where mobile charge carriers have diffused away, leaving fixed ions and creating an electric field that opposes further diffusion.

A circuit that converts alternating current into pulsating direct current, using one or more diodes arranged in half-wave, full-wave centre-tap or bridge configuration.

A heavily doped diode designed to operate safely in reverse breakdown, holding a nearly constant voltage across it, so it is used for voltage regulation and reference.

A three-terminal device with emitter, base and collector regions in which a small base current controls a much larger collector current, allowing current amplification and switching.

A transistor in which voltage applied to an insulated gate controls the conductivity of a channel between source and drain, giving very high input resistance.

Setting the steady direct-current voltages and currents at a transistor's terminals, using resistors, so the device works at a chosen operating point on its characteristic curves.

A widely used transistor bias arrangement in which two resistors from supply to ground set the base voltage, with an emitter resistor providing stability against temperature change.

A circuit of capacitors, inductors or resistors that removes unwanted ripple or frequency components from a signal, such as smoothing the output of a rectifier.

The ratio of the alternating ripple voltage to the direct output voltage of a power supply, expressing how smooth the rectified output is; smaller values mean better smoothing.

A circuit that increases the amplitude of a signal, usually by controlling a larger supply current with a small input, and is described by its gain, bandwidth and input impedance.

The ratio of an amplifier's output voltage to its input voltage, often expressed in decibels; it measures how many times the signal is enlarged.

A circuit that generates a continuous periodic waveform without an external input, using positive feedback and a frequency-selective network to set the output frequency.

A positional number system using only the digits zero and one, where each place represents a power of two; it is the natural language of digital circuits.

A set of rules for manipulating variables that take only the values zero and one, using operations AND, OR and NOT, used to simplify digital logic expressions.

A basic digital circuit that performs a logical operation on one or more binary inputs to produce a single output, such as AND, OR, NOT, NAND, NOR, XOR.

A table listing every possible combination of inputs to a logic circuit alongside the resulting output, used to define and verify its behaviour.

A bistable sequential circuit that stores one bit of data and changes state on a clock edge, forming the basis of registers and counters.

A handheld instrument that measures voltage, current and resistance, and often continuity and diode drop, selected by a rotary switch and connected through test probes.

A test instrument that displays a signal as a graph of voltage against time on a screen, letting the user measure amplitude, period, frequency and waveform shape.

An instrument that produces test waveforms of adjustable frequency, amplitude and shape, used to inject signals into circuits during testing and alignment.

Joining metal surfaces electrically and mechanically with a low-melting alloy, using a heated iron and flux so the solder wets the joint and forms a shiny connection.

An insulating board with copper tracks and pads that connect mounted components, replacing point-to-point wiring in almost all modern electronic equipment.

A soldered connection that looks dull, grainy or blobby because the joint was not heated enough or moved while cooling, causing intermittent or high-resistance contact.

A check with a multimeter that confirms a low-resistance path between two points, often signalled by a beep, used to trace broken tracks and faulty wires.

A circuit or integrated device that holds its output voltage constant despite changes in input voltage or load current, commonly using a Zener diode or a three-terminal IC.

A device of two or more coupled coils on a magnetic core that changes alternating voltage levels by mutual induction, stepping voltage up or down with little power loss.

Discarded electrical and electronic equipment and its parts, which contain valuable metals but also toxic substances and must be routed to authorised recyclers, never to ordinary bins.

The set of practices that prevent electric shock and fire, including switching off and isolating supply before work, using insulated tools and never touching live conductors.

Connecting exposed metal parts of equipment to the ground through a low-resistance path so fault current trips protection and touch voltage stays safe.

A deliberately weak wire or element in series with a circuit that melts and opens the circuit when current exceeds its rating, protecting wiring and equipment from overheating.

A written quotation given to a customer before repair work, listing the fault, the parts needed, labour charges and the expected time, protecting both parties.

The way a technician receives, advises and follows up with customers, covering polite communication, clear explanation of faults, honest pricing and keeping promised deadlines.

Earning a living by running one's own electronics service, repair or assembly business rather than working for an employer, requiring technical, financial and marketing skills.