🎯 2.1 — Use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V) and watt (W).
Understanding the correct units is fundamental. Click each card to reveal what it measures:
🎯 2.2 — Understand how insulation, double insulation, earthing, fuses, and circuit breakers protect the device or user.
Live wires are coated with an insulating material (e.g., plastic) that does not conduct electricity. This prevents accidental contact with the live wire, which could cause an electric shock.
Appliances with double insulation have an extra layer of insulating material between electrical components and the outer casing. They don't need an earth wire and are marked with this symbol:
Metal-cased appliances are earthed. If the live wire touches the casing, a large current flows to earth, blowing the fuse and making the appliance safe.
A fuse contains a thin wire that melts if the current exceeds a safe value, breaking the circuit. Fuses must be replaced once blown.
Circuit breakers are automatic switches that trip when they detect a fault. Unlike fuses, they can be reset. They react more quickly and are more sensitive.
Increase the current with the slider. When current exceeds the fuse rating, the wire heats up, glows, and snaps!
See how earthing and fuses protect you when a fault occurs. Click the button to trigger a fault!
💡 Example: A metal-cased toaster develops a fault where the live wire touches the casing. The earth wire carries the large fault current, blowing the fuse and disconnecting the supply — keeping you safe.
Click on each wire or button to learn about it. A UK plug has three pins connected to three colour-coded wires:
Select a component above to learn what it does and why it's important for safety.
🎯 2.3 — Understand why current in a resistor results in energy transfer and temperature increase, and domestic applications.
When electric current flows through a resistor, electrical energy is converted into heat. Flowing electrons collide with ions in the conductor, transferring kinetic energy. This increases the component's temperature.
This heating effect is used in: kettles, toasters, ovens, heaters, filament lamps, and hair dryers.
Watch electrons (blue) flow through the resistor wire. As current increases, electrons move faster, collide more with atoms (grey), and temperature rises!
💡 Example: The heating element in an electric kettle has a specific resistance. When current passes through it, it gets very hot, efficiently transferring thermal energy to the water.
🎯 2.4 — Know and use the relationship between power, current and voltage: P = I × V
Electrical power is the rate at which electrical energy is transferred. It equals the current multiplied by the voltage.
P = I × V
Power (Watts) = Current (Amps) × Voltage (Volts)
💡 Example: A lamp on a 230 V supply draws 0.2 A. Power = 0.2 × 230 = 46 W
Enter an appliance's power rating and supply voltage. We'll calculate the current drawn and recommend the correct fuse.
🎯 2.5 — Use the relationship between energy transferred, current, voltage and time: E = I × V × t
E = P × t = I × V × t
Energy (Joules) = Power (Watts) × Time (Seconds)
💡 Example: A 100 W bulb on for 2 hours: E = 100 × 7200 = 720,000 J = 720 kJ = 0.2 kWh
Work out how much it costs to run an appliance — just like your electricity bill!
🎯 2.6 — Know the difference between mains electricity being AC and direct current being supplied by a cell or battery.
DC flows in one direction only. Sources: batteries, cells, solar panels.
Think of DC as water flowing steadily in one direction through a pipe.
AC periodically reverses direction. Mains electricity is AC. In the UK/Europe: 50 Hz (changes direction 50 times per second). In North America: 60 Hz.
AC is advantageous because its voltage can be stepped up/down using transformers for efficient long-distance transmission.
Watch real-time animated waveforms! Adjust frequency and amplitude to see how AC differs from DC.
Test your understanding of mains electricity. Select an answer for each question and then check your results!