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 Gate – Inverts 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 Breakers – Automatic 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 Transformer – Increases voltage for efficient transmission over power lines.

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

• Step-Down Transformer – Reduces 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.