Unit 3/08A Electrical Science Principles Glossary List

Unit 308A (NELEC3/08A) Electrical Science & Principles Glossary

Outcome 1 – Mathematical Methods in Electrical Science

• Voltage (V) – Electrical potential difference.
• Current (I) – Flow of electric charge measured in amperes.
• Resistance (R) – Opposition to current flow.
• Power (P) – Rate of energy transfer (P = V × I).
• Energy (E) – Electrical energy consumed (E = P × t).
• Charge (Q) – Quantity of electricity (Q = I × t).
• Work Done (W) – Energy transferred electrically.
• Efficiency – Ratio of useful output to input.
• Prefixes – Multipliers (milli, micro, kilo, mega).
• Transposition – Rearranging formulas to isolate variables.
• Direct Proportion – When one value increases with another.
• Inverse Proportion – When one value increases as another decreases.
• Scientific Notation – Expressing numbers using powers of ten.
• Significant Figures – Precision of numerical values.
• Rounding – Adjusting numbers to required accuracy.
• Linear Relationship – Straight‑line relationship between variables.
• Graph Gradient – Rate of change between variables.
• Units (SI) – Standard measurement system.
• Conversion Factors – Used to change between units.

Outcome 2 – Electronic Components and Devices

• Diode – Allows current in one direction only.
• LED – Light‑emitting diode.
• Zener Diode – Allows reverse conduction at set voltage.
• Transistor – Semiconductor used for switching/amplification.
• Resistor – Limits current flow.
• Variable Resistor – Adjustable resistance.
• Potentiometer – Three‑terminal adjustable resistor.
• Capacitor – Stores electrical charge.
• Electrolytic Capacitor – Polarised high‑value capacitor.
• Inductor – Coil storing energy in magnetic field.
• Relay – Electrically operated switch.
• Solenoid – Electromagnetic actuator.
• Transformer – Changes AC voltage levels.
• Rectifier – Converts AC to DC.
• Bridge Rectifier – Four‑diode AC‑DC converter.
• Smoothing Capacitor – Reduces ripple in DC supplies.
• Sensor – Device detecting physical changes.
• Thermistor – Temperature‑dependent resistor.
• LDR – Light‑dependent resistor.
• IC (Integrated Circuit) – Miniaturised electronic circuit.

Outcome 3 – Alternating Current (AC) Circuits

• AC (Alternating Current) – Current that changes direction periodically.
• Frequency (Hz) – Cycles per second.
• Period (T) – Time for one cycle.
• Amplitude – Peak value of AC waveform.
• Peak Voltage (Vpeak) – Maximum instantaneous voltage.
• RMS Voltage (VRMS) – Effective AC voltage.
• Phase Angle – Angular difference between waveforms.
• Inductive Reactance (XL) – Opposition from inductors (XL = 2πfL).
• Capacitive Reactance (XC) – Opposition from capacitors (XC = 1/(2πfC)).
• Impedance (Z) – Total AC opposition.
• Power Factor – Ratio of real to apparent power.
• Real Power (kW) – Useful power.
• Reactive Power (kVAR) – Power stored and returned.
• Apparent Power (kVA) – Combined real + reactive
• Resonance – When XL = XC.
• Harmonics – Distortion from non‑linear loads.
• Three‑Phase Supply – System with three AC waveforms 120° apart.
• Phase Sequence – Order of phase rotation.

Outcome 4 – Luminaires and Lighting Principles

• Luminaire – Complete lighting unit.
• Lamp – Light‑producing element.
• Luminous Flux (lumens) – Total light output.
• Illuminance (lux) – Light falling on a surface.
• Luminous Intensity (candela) – Light in a specific direction.
• Colour Temperature (K) – Warm/cool appearance.
• CRI (Colour Rendering Index) – Accuracy of colour reproduction.
• Efficacy (lm/W) – Light output per watt.
• Glare – Excessive brightness causing discomfort.
• Diffuser – Spreads light evenly.
• Ballast – Controls current in discharge lamps.
• Driver – Controls LED power.
• Emergency Luminaire – Provides light during power failure.
• IP Rating – Protection against dust/water.
• Lux Level Requirements – Recommended lighting standards.

Outcome 5 – DC Machines and AC Motors

• DC Motor – Converts DC to mechanical rotation.
• Armature – Rotating part of a motor.
• Field Windings – Produce magnetic field.
• Commutator – Reverses current direction in DC motors.
• Brushes – Conduct current to rotating parts.
• Induction Motor – AC motor using rotating magnetic fields.
• Rotor – Rotating component.
• Stator – Stationary magnetic field component.
• Slip – Difference between synchronous and rotor speed.
• Synchronous Speed – Ns = 120f/p.
• Torque – Rotational force.
• Starting Current – High initial current in motors.
• Star‑Delta Starter – Reduces starting current.
• Single‑Phase Motor – Uses one AC supply.
• Three‑Phase Motor – Uses three AC supplies.

Outcome 6 – Operating Principles of Electrical Components

• Fuse – Element melts under fault current.
• MCB (Miniature Circuit Breaker) – Trips under overload/short circuit.
• RCD (Resisual Current Device) – Detects current imbalance between line and neutral.
• RCBO – Combines MCB and RCD.
• Contactor – Heavy‑duty switch.
• Overload Relay – Protects motors from overheating.
• Isolator – Manually operated switch for safety.
• SPD (Surge Protection Device) – Protects against voltage spikes.
• Enclosure – Housing for electrical components.
• Terminal Block – Connection point for conductors.
• Busbar – Conductive bar distributing power.
• Pilot Light – Indicates equipment status.
• Pushbutton – Manual control switch.
• Limit Switch – Detects mechanical movement.

Outcome 7 – Electric Heating Principles

• Joule Heating – Heat produced by current.
• Specific Heat Capacity – Energy needed to raise temperature.
• Thermal Conductivity – Ability to transfer heat.
• Conduction – Heat transfer through solids.
• Convection – Heat transfer through fluids.
• Radiation – Heat transfer via electromagnetic waves.
• Heating Load – Required power to raise temperature.
• Immersion Heater – Electric water heater.
• Storage Heater – Stores heat for later release.
• Heat Pump – Transfers heat using refrigeration cycle.
• Thermostat – Temperature‑control device.
• Element – Resistive heating component.
• Insulation – Reduces heat loss.
• Thermal Lag – Delay in temperature change.