NABTEB Automobile Electrical Works flashcards
NABTEB Automobile Electrical Works · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Ohm's law
- The relationship V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. Used to calculate any one value when the other two are known.
- Series circuit
- 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 them.
- Parallel circuit
- A circuit in which components are connected across the same two points so each receives the same voltage. Total resistance is less than the smallest branch resistance.
- Short circuit
- An unintended low-resistance path that bypasses the load, causing excessive current flow. It usually blows a fuse or trips a circuit breaker and may damage wiring.
- Electrical power
- The rate of energy transfer, calculated as P = V × I, P = I²R, or P = V²/R. Power is measured in watts and indicates the load on a circuit.
- Battery capacity in Ah
- The ampere-hour rating is the current a battery can deliver for a stated time at the 20-hour rate. A 60 Ah battery delivers 3 A for 20 hours.
- Specific gravity
- The density of battery electrolyte compared with water. A fully charged lead-acid cell reads about 1.265, while 1.120 or lower indicates heavy discharge.
- Alternator rectifier
- A six-diode bridge that converts the three-phase alternating current produced by the alternator into direct current for charging the battery and supplying vehicle loads.
- Voltage regulator
- A device that controls alternator field current so charging voltage stays within about 13.8–14.5 V regardless of engine speed or electrical load.
- Cold cranking amps
- The current a battery can deliver for 30 seconds at −18 °C while maintaining at least 7.2 V. It indicates the battery's ability to crank a cold engine.
- Starter solenoid
- An electromagnetic switch that engages the starter drive with the flywheel ring gear and closes heavy contacts to feed current to the starter motor.
- Starter voltage drop test
- A cranking test that measures battery voltage while the engine is cranked. Voltage should remain above about 9.6 V at 20 °C; lower values indicate a weak battery or high-resistance cables.
- One-way clutch drive
- A sprag clutch in the starter drive that transmits torque from the motor to the engine but freewheels when the engine starts, preventing the armature from being driven.
- Ignition coil
- A transformer with primary and secondary windings that steps up battery voltage to the high voltage needed to jump the spark plug gap when primary current is interrupted.
- Dwell angle
- The number of distributor degrees during which the primary ignition circuit is closed. Too little dwell weakens the spark; too much overheats the coil.
- Ignition timing
- The point in the engine cycle at which the spark occurs, usually stated in degrees before top dead centre. It advances with speed and retards with load.
- Spark plug heat range
- A rating of how quickly a plug dissipates heat. Hot plugs suit low-speed engines; cold plugs suit high-speed, high-load engines to prevent pre-ignition.
- Firing order
- The sequence in which cylinders receive spark, for example 1-3-4-2 on a four-cylinder in-line engine. Correct order prevents cross-firing and rough running.
- Headlamp relay
- A relay used to switch the high current of headlamps. The dash switch operates only the relay coil, reducing current through the switch and its wiring.
- Indicator flasher rate
- Direction indicators must flash at 60–120 flashes per minute. A faster than normal flash usually indicates a failed bulb on that side of the circuit.
- Brake light switch
- A pedal-operated switch that feeds the stop lamps. A faulty switch causes no brake lamps while tail lamps continue to work normally.
- Blade fuse colour code
- Standard colour coding for blade fuses: 5 A tan, 7.5 A brown, 10 A red, 15 A blue, 20 A yellow, 25 A clear, 30 A green.
- Automotive relay terminals
- Standard relay numbering: 30 is supply, 85 and 86 are the coil, 87 is the normally open output, and 87a is the normally closed output.
- Fusible link
- A short section of special wire fitted in a main feed that melts before the main cable is damaged. It protects high-current circuits that a blade fuse cannot handle.
- Earth return
- A system in which the vehicle body or chassis forms the return path to the battery negative. A poor earth causes dim lamps or erratic operation of several circuits.
- Wiper park switch
- A switch inside the wiper motor that keeps the motor running after the control is switched off until the blades reach their rest position.
- Parasitic drain
- Current drawn from the battery when all accessories are switched off. More than about 50 mA indicates a fault that will flatten the battery overnight.
- Diagnostic trouble code
- A code stored by an electronic control module when it detects an out-of-range signal. The code identifies the affected circuit, not necessarily the faulty component.
- Voltage drop testing
- Measuring the voltage lost across a cable, connection, or component while current flows. More than 0.1 V across an earth connection indicates excessive resistance.
- Digital multimeter
- An instrument that measures voltage, resistance, current, and continuity. The correct function and range must be selected before probing a circuit.
- Battery safety
- Batteries contain sulphuric acid and give off hydrogen when charging. Wear eye protection, avoid sparks and flames, and charge in a ventilated area.
- DIN terminal 30
- The standard designation for battery positive supply in automotive wiring. Related codes include 31 for earth, 15 for ignition, and 50 for starter control.