Chapter 5 - Electricity in the Home Flashcards
Define direct current.
- Current which flows in one direction only.
Define alternating current.
- Current which reverses its direction of flow.
Give the mains frequency of the UK.
- 50Hz (hertz)
What does every mains circuit contain?
- A live wire alternating positive and negative charge.
- A neutral wire at zero volts.
Explain the use of step-up transformers in the national grid.
- Step-up transformers increase the size of the alternating p.d much bigger, so less current is needed to transfer the amount of power, and to reduce current loss via heat.
Give the definition of the national grid.
- A nationwide network of cables and transformers.
How do step-down transformers supply electricity to consumers?
- These transformers step-down the voltage and supply the power to homes and other places nationwide.
What is the mains voltage in the UK?
- 230V
State the colours of the three wires found in a three-pin plug.
Live wire - Brown
Neutral wire - Blue
Earth wire - Green Yellow Strips
Explain the purpose of plastic for plugs.
- Plastic is used as it is a good electrical insulator.
Explain the use of an earth wire in a 3-pin plug.
- Stays at 0 volts
- Only carries current during a fault
Too much current of 5V has passed through a wire.
What would you place in the 3-pin plug to cut the circuit off the next time it happened?
Explain your answer. [4]
- Fuse [1]
- When too much current passes through the wire [1]
- The fuse melts [1]
- Breaks the circuit. [1]
Joe wants to make an efficient wire for his 3-pin plug, but only has 3 metals at his disposal:
- Brass
- Tin
- Copper
Which one should Joe choose to make his wires?
Explain your answer [3]
- Copper (for wires) [1]
- Good electrical conductor [1]
- Bends easily [1]
Give the equation that links Power, Time and Energy Transferred.
E = P x T
What is the power supplied to a device?
- Energy transferred to it each second.
