NITA Auto Electrician Trade Test key terms

The fixed relationship in a resistive circuit where voltage equals current multiplied by resistance, and current equals voltage divided by resistance. It lets a technician predict one value when the other two are known or measured.

A circuit where components are connected end to end so the same current flows through every part. Total resistance is the sum of the individual resistances and a single break stops current everywhere.

A circuit where components are connected across the same two points so each receives the full supply voltage while sharing total current. Total resistance is always lower than the smallest individual branch resistance.

The loss of potential along a conductor or component caused by its resistance while current flows. Excessive drop in a supply or earth path indicates poor connections, undersized cable or corrosion.

The production of a voltage in a conductor whenever it experiences a changing magnetic field. This principle underlies generators, ignition coils, alternators, transformers and many vehicle sensors.

A rechargeable battery using lead plates and dilute sulfuric acid electrolyte that delivers high cranking current. Each cell produces about two volts, so a twelve-volt battery contains six cells connected in series.

The current a battery can deliver for thirty seconds at minus eighteen degrees Celsius while staying above a specified terminal voltage. It is the main rating for judging whether a battery can crank a cold engine.

The amount of usable capacity remaining in a battery expressed as a percentage of full charge. It is estimated from open-circuit voltage, electrolyte specific gravity or a dedicated battery monitor.

The build-up of hard lead sulfate crystals on battery plates caused by leaving a battery discharged or undercharged. It reduces capacity and cranking ability and may become permanent if not corrected early.

A tool that draws electrolyte from a battery cell and floats a bulb to show specific gravity. Comparing cell readings reveals state of charge and identifies a weak or failed cell.

An engine-driven generator that produces alternating current, rectifies it to direct current and holds system voltage near a regulated set point. It recharges the battery and powers electrical loads while the engine runs.

A control device that limits alternator output voltage to a safe target, typically around fourteen volts, by adjusting field current. It prevents overcharging while keeping the battery charged under varying loads and speeds.

A measurement of the small alternating voltage superimposed on a direct current charging output, usually read with a multimeter set to AC volts. High ripple points to failed alternator diodes or a poor connection.

A heavy-duty series-wound electric motor that turns the engine flywheel through a drive pinion during starting. It draws very high current, so cable size, connections and battery condition are critical.

An electromagnetically operated switch that uses a movable plunger to close heavy contacts. In starting systems it also physically engages the cranking motor pinion with the flywheel ring gear.

The correct vertical and horizontal setting of a headlamp beam so the road ahead is lit without dazzling oncoming drivers. It is checked on a beam setter or against a wall at a specified distance.

A system that adjusts headlamp angle to compensate for vehicle load, either manually by a dash control or automatically through body height sensors. It keeps the beam pattern correctly aimed when the rear is loaded.

A rating in kelvin describing the colour appearance of light emitted by a lamp, from warm yellow to cool blue-white. It does not by itself indicate brightness, which is measured in lumens.

A semiconductor light source that produces light when current passes through a junction, offering low current draw and long life. Its polarity matters and it often needs a driver or ballast resistor.

A step-up transformer with a low-resistance primary winding and a many-turn secondary winding. Collapsing primary current induces a very high secondary voltage that jumps the spark plug gap.

The number of distributor degrees, or the time period, during which the primary ignition circuit is closed and coil current builds. Too little dwell weakens the spark; too much overheats the coil.

The moment, measured in crank degrees before or after top dead centre, when the spark occurs. Correct timing balances power, fuel economy and knock avoidance across engine speed and load.

A rating of how quickly a spark plug sheds heat from its tip to the cylinder head. A plug too hot for the engine risks pre-ignition, while one too cold fouls and misfires.

A bundled assembly of insulated conductors, terminals and connectors routed through a vehicle to carry power, ground and signals. It is protected by loom tape, conduit and clips to resist chafing and heat.

The metal contact crimped or soldered to a conductor end that mates with a corresponding contact inside a housing. Correct crimp height, seal and locking tang prevent high resistance and intermittent faults.

The maximum current a fuse is designed to carry continuously before its element melts and opens the circuit. It must be chosen to protect the cable, not simply to match the load.

An electrically operated switch in which a small coil current closes contacts that carry a much larger load current. It allows thin control wiring and low-current switches to control heavy circuits.

A resettable protective device that opens a circuit when current exceeds its rating, often using a bimetallic strip. Unlike a fuse it can be reset, but the underlying overload must still be found.

A handheld instrument that measures voltage, resistance, current and often continuity or diode drop. Choosing the correct function and range, and the right probe placement, is essential to avoid damage or false readings.

A test instrument that displays voltage against time, revealing the shape and timing of rapidly changing signals. It is used to inspect injector pulses, sensor waveforms, ignition patterns and network data.

A meter accessory that encircles a conductor and measures current from its magnetic field without breaking the circuit. It is ideal for checking cranking current, alternator output and parasitic drain.

A procedure that measures current flowing with all accessories off and modules asleep to find an unexpected battery load. Excessive drain is found by measuring total current then isolating circuits or fuses.

A microprocessor-based module that reads sensor inputs, runs control strategies and drives actuators through output stages. It stores diagnostic trouble codes and communicates with other modules over a network.

A two-wire differential serial network that lets control modules exchange data without dedicated wiring for every signal. Faults are traced by checking bus resistance, voltage levels and termination.

A stored alphanumeric identifier set when a module detects a fault in a monitored circuit or system. The code points to an area to test, not directly to the component to replace.

A sensor with a coil and permanent magnet that generates an alternating voltage as a toothed wheel passes it. It needs no supply voltage but produces a signal that grows with speed.

A device that reports crankshaft speed and angular position to the engine control module. Its signal is essential for ignition timing and fuel injection synchronisation.

A piezoelectric sensor bolted to the engine block that produces a voltage when it detects the vibration of detonation. The module then retards ignition timing to protect the engine.

An output device such as a motor, solenoid, injector or relay that converts an electrical command from a control module into physical action. Its circuit can be tested for supply, ground and control signal.

A control method that switches a supply on and off rapidly and varies the proportion of on-time to control average power. It is used for fuel injectors, blower motors, lamps and solenoid valves.

A direct-current motor in which electronic switching replaces mechanical brushes and commutator, usually using permanent magnets on the rotor. It needs a driver that senses rotor position to commutate the windings.

A semiconductor device that produces a voltage when a magnetic field acts on it, often used to detect rotation or position without contact. It requires a supply and gives a clean switching or analogue output.

A safety procedure that isolates energy sources and attaches a personal lock and warning tag before work begins. It prevents accidental starting or energising of equipment while a technician is working on it.

Wearable protection such as safety glasses, insulated gloves, hearing protection and footwear selected for the task. It reduces injury risk but does not replace safe procedures or guarding.

A structured look at a task that identifies hazards, judges how likely and severe harm could be, and records controls before work starts. It should be reviewed whenever conditions or tasks change.

The safe isolation of a vehicle battery, usually by removing the earth terminal first, before electrical work or welding. It protects the technician and prevents damage to modules and wiring.

A drawing that shows electrical components and the conductors connecting them, using standard symbols and often a grid reference. It shows electrical relationships rather than the physical layout of parts.

A standardised graphic used on schematics to represent a component such as a battery, switch, resistor or earth. Recognising symbols quickly is essential for reading diagrams and tracing faults.

A circuit path in which the vehicle body or chassis carries current back to the battery negative terminal instead of a dedicated wire. Poor body connections here cause many intermittent electrical faults.

The relationship where electrical power in watts equals voltage multiplied by current, and also equals current squared times resistance. It is used to size cables, fuses and alternator capacity for added loads.

A diagnostic device that communicates with vehicle modules to read fault codes, live data and actuator tests. Its usefulness depends on correct interpretation of data rather than code reading alone.

A sensor that reports suspension position to a module for headlamp levelling or air suspension control. It typically uses a potentiometer or Hall element linked by a small arm to the suspension.