Electrical Systems GCSE AQA Engineering

1. Basic Electrical Principles

  • Current (I) – The flow of electric charge in a circuit, measured in amperes (A).

  • Voltage (V) – The potential difference between two points, measured in volts (V).

  • Resistance (R) – The opposition to current flow, measured in ohms (Ω).

  • Power (P) – The rate of energy transfer, measured in watts (W) (P = VI).

  • Charge (Q) – The amount of electric charge in coulombs (C), Q = It.


2. Electrical Components & Their Functions

  • Resistor – Limits the current flow in a circuit.

  • Capacitor – Stores and releases electrical energy (used in timing circuits).

  • Inductor – Stores energy in a magnetic field (used in filters and transformers).

  • Diode – Allows current to flow in only one direction (used in rectifiers).

  • LED (Light Emitting Diode) – A diode that emits light when current flows through it.

  • Transistor – A switch or amplifier used in digital circuits.

  • Relay – An electrically controlled switch used for high-power applications.

  • Transformer – Changes AC voltage levels (used in power supplies).


3. Ohm’s Law & Electrical Calculations

  • Ohm’s Law – V = IR (Voltage = Current × Resistance).

  • Power Equation – P = VI (Power = Voltage × Current).

  • Energy Equation – E = Pt (Energy = Power × Time).

  • Resistance in Series – R_total = R₁ + R₂ + R₃...

  • Resistance in Parallel – 1/R_total = 1/R₁ + 1/R₂ + 1/R₃...


4. Circuit Types & Configurations

  • Series Circuit – Components are connected end-to-end (same current, shared voltage).

  • Parallel Circuit – Components are connected across each other (same voltage, shared current).

  • Combination Circuit – A mix of series and parallel components.


5. AC vs. DC Electricity

  • Direct Current (DC)Steady, constant voltage (used in batteries).

  • Alternating Current (AC)Voltage changes direction periodically (used in mains electricity).

  • Frequency (Hz) – The number of AC cycles per second, UK mains is 50 Hz.


6. Sensors & Control Systems

  • LDR (Light Dependent Resistor) – Resistance changes with light levels (used in automatic lighting).

  • Thermistor – Resistance changes with temperature (used in thermostats).

  • Switches – Turn circuits on or off (e.g., push-button, toggle, reed switch).

  • Microcontroller – A programmable chip that controls electronic systems.


7. Logic Gates & Digital Circuits

  • AND Gate – Outputs 1 only when both inputs are 1.

  • OR Gate – Outputs 1 when at least one input is 1.

  • NOT GateInverts the input (1 → 0, 0 → 1).

  • NAND & NOR Gates – Variations of AND/OR gates with inverted outputs.

  • Truth Tables – Show how logic gates respond to inputs.


8. Electrical Safety & Protection Devices

  • Fuses – Thin wire melts if current is too high, breaking the circuit.

  • Circuit BreakersAutomatic switch that trips if current is too high.

  • Earthing – Provides a safe path for excess current (prevents shocks).

  • Double Insulation – Protects users by having two layers of insulation.

  • RCD (Residual Current Device) – Cuts off power if a leakage is detected.


9. Power Generation & Distribution

  • Power Station – Generates electricity from fossil fuels, nuclear, or renewables.

  • Step-Up TransformerIncreases voltage for efficient transmission over power lines.

  • National Grid – Transports electricity at high voltage, low current to reduce losses.

  • Step-Down TransformerReduces voltage for safe use in homes (e.g., 230V in the UK).

  • Battery Storage – Stores DC energy for portable devices.


10. Renewable & Non-Renewable Energy Sources

  • Coal/Oil/Gas Power – Uses fossil fuels to heat water, create steam, and turn turbines.

  • Nuclear Power – Uses nuclear fission to generate heat for turbines.

  • Solar Power – Converts sunlight into electricity (photovoltaic) or heat.

  • Wind Power – Uses wind turbines to generate AC electricity.

  • Hydropower – Uses moving water to turn turbines for electricity.

  • Geothermal Energy – Uses heat from the Earth’s core to generate steam.

  • Biomass Energy – Burns organic materials to release energy.


11. Efficiency & Energy Storage

  • Efficiency Equation – Efficiency (%) = (Useful Energy Output / Total Energy Input) × 100.

  • Pumped Storage – Uses excess electricity to pump water uphill for later use.

  • Flywheel Energy Storage – Stores energy in a rotating mass.

  • Supercapacitors – Store energy quickly but for short durations.


12. Electrical Engineering Applications

  • Robotics – Uses electrical systems for control and movement.

  • Automotive Electronics – Electric vehicles (EVs), sensors, and control systems.

  • Smart Technology – Internet of Things (IoT) devices use sensors and microcontrollers.

  • Communication Systems – Use radio waves, Wi-Fi, and fiber optics to transmit data.