This definitions covers Key Definitions within Mains Electricity & Safety for GCSE Physics. Revise Mains Electricity & Safety in Electricity for GCSE Physics with 18 exam-style questions and 30 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 8 of 16 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
📖 Key Definitions
Alternating current (AC): Electric current that continuously reverses direction. UK mains: 50 Hz (reverses 50 times per second), 230 V.
Direct current (DC): Electric current that flows in one direction only. Provided by batteries and DC power supplies.
Live wire (brown): Carries the supply voltage to the appliance. Alternates between approximately +325 V and -325 V. Always potentially lethal.
Neutral wire (blue): Completes the circuit back to the supply. At approximately 0 V.
Earth wire (green and yellow): Safety wire connected to the metal casing of appliances. Normally carries no current; provides low-resistance escape path in case of a fault.
Fuse: A thin wire that melts if the current exceeds its rating, breaking the circuit and cutting off the power supply.
Double insulation: Appliances with non-conducting (plastic) outer casings that do not require an earth wire for safety.
Practice questions for Mains Electricity & Safety
What does AC stand for, and how does it differ from DC?
Explain how a fuse protects an electrical circuit from damage.