P5 - Electricity in the home Flashcards
(29 cards)
Frequency and voltage of mains electricity in the UK?
50Hz
230V
What does a cell or battery provide?
- Direct current
- Current only flows in one direction
- Produced by direct potential difference
What does mains electricity provide?
- Alternating current
- Current repeatedly reverses direction and is produced by an alternating potential difference
Colour of live wire covering?
Brown
Colour of neutral wire covering?
Blue
What colour is the earth wire covering?
Green and yellow stripes
What does live wire do?
- Carries the alternating potential difference from the supply
- Dangerous because it has a high potential difference of 230V
- Large current would flow if touched
What happens if the live wire inside an appliance touches the neutral wire?
- Very large current flows
- Called a short circuit
- Fuse melts and disconnects the live wire from the mains, keeps the appliance safe
What does the neutral wire do?
Completes the circuit
What does the earth wire do?
- Safety wire to stop the appliance becoming live
- Only carries the current when there is a fault
Why is plastic used for the wire coatings and plug case?
- Good electrical insulator
- Copper is used for the wires because it is a good electrical conductor and bends easily
Equation for power in terms of resistance?
Power= (current)2 * resistance
What is the equation for power in terms of potential difference?
power = potential difference * current
What are electrical appliances designed for?
- Bring out energy transfers
- The amount of energy an appliance transfers depends on how long the appliance is switched on for and the power of the appliance
What happens within an airdryer?
- Transfers energy electrically from a chemical store to the kinetic energy store of the fan inside the hairdryer and to the thermal energy store of the heating filaments
What happens when you turn an electrical appliance on?
The potential difference of the mains supply causes charge(carried by electrons) to flow through it
What is the equation for energy transferred?
Energy transferred=power* time
What is the other equation for energy transferred?
Energy transferred=charge flow * potential difference
What is the equation for charge flow?
Charge flow = current*time
What is the national grid?
The National Grid is a system of cables and transformers linking power stations to consumers
What do step up transformers do?
Used to increase the potential difference from the power station tot he transmission cables
What do step down transformers do?
Used to decrease to a much lower value the potential difference for domestic use
Why is the national grid efficient?
It uses high voltage and low current, minimizing energy loss due to heat in the transmission lines
