Assam ASSEB HS Skill Subject Electronics and Hardware key terms

The electrical potential difference between two points in a circuit, measured in volts. It is the push that drives charge through a conductor and is often called potential difference or electromotive force.

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

The opposition a material offers to the flow of electric current, measured in ohms. Higher resistance allows less current for a given applied voltage.

The relationship stating that current through a conductor equals voltage divided by resistance (I = V/R). It lets you calculate any one of the three quantities when the other two are known.

A circuit in which components are connected end to end so the same current flows through each. Total resistance is the sum of individual resistances and voltage divides across the components.

A circuit in which components are connected across the same two nodes, so each receives the same voltage while current divides among the branches. Total resistance is always less than the smallest branch resistance.

Two rules for analysing circuits: the current law says charge entering a junction equals charge leaving it, and the voltage law says voltages around any closed loop sum to zero.

A network of two or more resistors in series used to obtain a fraction of the input voltage. Output voltage equals input voltage multiplied by the ratio of the lower resistor to the total.

The ability of a component to store electric charge per unit of applied voltage, measured in farads. Capacitance depends on plate area, separation and the dielectric material between the plates.

A passive two-terminal component that limits current and creates voltage drops. Fixed types use colour bands or printed codes to show value and tolerance, while variable types include potentiometers and thermistors.

A component that stores energy in an electric field between two conductive plates separated by a dielectric. It blocks direct current while allowing alternating current to pass, and is rated by capacitance and voltage.

A semiconductor device with a p-n junction that conducts current mainly in one direction. It is used for rectification, protection against reverse polarity and signal clamping.

The condition where the anode of a diode is made more positive than the cathode, allowing current to flow readily. The voltage drop is about 0.7 V for silicon and 0.3 V for germanium devices.

The condition where the cathode of a diode is made more positive than the anode, so only a tiny leakage current flows. Exceeding the rated reverse voltage causes breakdown and possible damage.

A diode designed to operate safely in reverse breakdown at a specified voltage. It is widely used as a simple shunt voltage regulator and as a reference in protection circuits.

A three-terminal semiconductor device with base, collector and emitter in which a small base current controls a larger collector current. It works as a switch or amplifier in NPN and PNP versions.

A transistor in which an electric field at the gate controls current flow between source and drain. It draws almost no gate current, making it popular for low-power switching and analogue circuits.

Setting the steady direct-current voltages and currents at a transistor's terminals so it operates at a suitable point on its characteristic curves. Correct bias prevents distortion and keeps the device within ratings.

A circuit that converts alternating current into pulsating direct current using diodes. Half-wave designs use one diode, while full-wave and bridge designs use two or four diodes for better efficiency.

A base-2 numbering system using only the digits 0 and 1, where each position represents a power of two. It is the natural language of digital circuits and processors.

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

A table listing every possible combination of inputs to a logic circuit alongside the resulting output. It is used to verify behaviour and derive or simplify logic expressions.

A mathematical system for manipulating binary variables using operations AND, OR and NOT. Rules such as De Morgan's theorems allow logic circuits to be simplified and built with fewer gates.

A bistable digital storage element that holds one bit of data until clocked or set. Types include SR, D, JK and T, and they form the basis of registers and counters.

A chain of flip-flops that moves data one bit per clock pulse, used for serial-to-parallel or parallel-to-serial conversion. It can also delay or store digital data.

A combinational logic device that selects one of several data inputs and routes it to a single output according to selection lines. It is used for data routing and signal sharing.

A single integrated circuit containing a processor core, memory and programmable input/output peripherals. It is used to control devices and is programmed in embedded firmware for dedicated tasks.

A computer system built into a larger device to perform a dedicated function, often with real-time constraints. Examples include washing machine controllers, vehicle engine units and medical monitors.

Software stored in non-volatile memory on a microcontroller or device that controls its low-level operation. It is usually written once by the manufacturer and may be updated by flashing.

General-purpose input/output pins on a microcontroller that the programmer can configure as digital inputs or outputs. They connect the chip to switches, LEDs, relays and sensors.

A technique of switching a digital output rapidly on and off to control average power delivered to a load. It is used for dimming LEDs and varying motor speed.

A circuit that converts a continuous analogue voltage into a discrete digital number for processing. Resolution is given in bits, and sampling rate determines how fast signals can be captured.

A handheld instrument that measures voltage, current, resistance and often continuity or capacitance. Digital types show readings on an LCD and require correct range and probe socket selection.

An instrument that displays how a signal voltage varies with time on a screen. Controls for time base, vertical scale and trigger let you observe waveform shape, frequency and amplitude.

A check that confirms a low-resistance path exists between two points, usually signalled by a beep. It is used to verify wiring, fuses and PCB traces without applying power.

The process of joining metal parts with a low-melting-point alloy that wets the surfaces without melting them. Good joints are shiny and smooth, indicating proper heat and flux action.

A chemical agent applied during soldering to remove oxide films and help molten solder wet the joint. Residue should be cleaned where it could corrode or cause leakage.

A dull, grainy or cracked connection caused by insufficient heat or movement while solder solidified. It produces intermittent faults and should be reflowed with fresh flux and proper heat.

An insulating board with patterned copper tracks that connect mounted components. It replaces point-to-point wiring and is designed with layers, pads and vias for reliable assembly.

A protective polymer coating applied over a printed circuit board, leaving pads exposed for soldering. It prevents solder bridges and protects copper tracks from oxidation and contamination.

An unwanted blob of solder connecting two adjacent pads or tracks, creating a short circuit. It is removed with solder wick or a desoldering pump and then inspected.

A braided copper strip used with flux and a hot iron to draw excess solder away from a joint or bridge. It is a standard tool for repair and rework on circuit boards.

The main circuit board of a computer that carries the CPU socket, memory slots, chipset and expansion connectors. It links all major components and distributes power and data signals.

Random access memory is volatile working storage that holds programs and data currently in use. It loses contents when power is removed and is installed in slots on the motherboard.

A component that converts mains alternating current into regulated direct-current rails for a computer. Ratings such as wattage and efficiency determine how much load it can safely support.

The sudden transfer of static charge between objects, which can destroy sensitive semiconductor devices. Anti-static wrist straps, mats and bags are used to prevent damage during handling.

Power-on self-test is the diagnostic routine a computer runs at startup to check hardware such as memory and graphics. Beep codes or error messages indicate faults found during the test.

A small coin cell on the motherboard that keeps the real-time clock and basic settings alive when power is off. A flat cell causes lost time and configuration errors at boot.

A heat-conducting compound applied between a processor and its heatsink to fill microscopic air gaps. It improves heat transfer and must be cleaned and reapplied when a cooler is remounted.