Electricity P2 Flashcards
What type of current do car batteries dry cells and solar cells have?
Direct
How do power stations sometimes produce electricity? What type of current is this ?
Via magnets. Alternating current
What does the UK mains electricity supply generate a frequency of?
50 hertz (Hz)
What does the UK mains electricity supply deliver electricity at ?
230Volts (V)
What is the function of outer insulation in the plug?
All three wires in the cable are bundled together with an extra plastic insulation wrapped around them for safety
What does the cable grip do in a plug?
It holds the cable tightly in place, so wires don’t come loose
What is the function of the live wire within a plug?
Is a copper wire with brown plastic along where the current enters the device?
What colour is the live wire?
Brown
What is the function of the fuse?
Is a glass or ceramic canister containing a thin wire that melts if the current is too high
Function of the neutral wire
Is a copper wire coated in blue plastic that connects the cable in the wall to complete the circuit
What colour is the neutral wire?
Blue
What is the function of the earth wire?
It is a copper wire coated in green and yellow striped plastic that provides a path for the current to flow from the case of the device to the ground. In the chance there is a fault.
What is the colour of the earth wire?
Green and yellow (striped)
What does 50 Hz actually mean?
The current changes direction and back again 50 times/s
What does the live wire carry?
Alternating potential difference from the electricity supply
What is the voltage like in the Earth wire and why?
It is at 0 V since it only carries a current if there is a fault
What does the Earth wire provide?
A low resistance path to the ground
What is voltage like in the neutral wire?
Pretty close to 0 V
What would happen if the live wire was loose and we had no earth wire?
The next person to touch the plug would be electrocuted
What does the fuse do and why?
If there is a fault that causes the casing of device to become live a large current flows through the low resistance earth wire causing the fuse to melt and break the circuit
What is the equation that links energy power and time?
Energy equals power times time, E= PxT
What is the equation linking potential difference power and current?
Power= potential difference x current, P=VxI
What does the national grid do?
Distribute electricity across the country it connects power stations to homes workplaces and buildings. The electricity may be produced by conventional power generator station turning on a generator or another way.
What do pylons do?
They carry electricity cables high above the ground
What is a transformer?
A device that changes the potential difference of voltage of an electrical supply in transmission lines
What is a step up transformer?
Increases the voltage from about 25,000 V to 400,000 V and decreases the current
What is a step down transformer?
Decreases the voltage and increases the current
When is a step up transformer used and why?
Before the electrical power leaves a power station it goes for a step up transformer to a volt 400,000 V to save money and energy
What happens when electrical power reaches a local area?
It goes for a step down transformer to around 230 V for domestic use
What is the equation to check if a transformer is 100% efficient?
Potential difference across primary coil x current in primary coil = potential difference across secondary coil x current in secondary coil
How are the cables adapted to ensure minimum amount of power is lost/ dissipated ?
Theyre thick so the resistance is low and they are high voltages used to reduce current through transmission lines
