C4 Supplying Electricity Flashcards
Power stations generate electricity with what type of current
Alternating
What devices on the national grid are used to increase and decrease potential difference
Step up / Step down
What is the maximum voltage of overhead cables on the national grid
400,000V
Equation relating power, current and potential difference
Power (watts) = current (amps) x potential difference (volts)
Equation relating power, current and resistance
Power (watts) = current^2 (amps) x resistance (ohms)
Equation used to work out unknown values on transformers
Primary potential difference (Volts) x Primary current (amps) = Secondary potential difference (Volts) x Secondary current (amps)
Equation relating charge flow and time
Charge flow (Coulombs) = Current (Amps) x time (Seconds)
Equation relating energy transfer, charge flow and potential difference
Energy transferred (Joules) = Charge flow (Coulombs) x Potential Difference (Volts)
Equation relating power, energy and time
Power (Watts) = Energy transferred (Joules) / time (seconds)
What is the potential difference supplied to buildings from the national grid
230V
What kind of current does a battery/cell supply (AC/DC)
Direct Current
What kind of current does a mains power supply, supply (AC/DC)
Alternating current
Frequency of the mains electricity in the UK
50Hz
Colour of the earth wire
Green and yellow striped
Purpose of the earth wire
The potential difference of the earth wire is 0V so if there is a fault and the live wire is touching the casing, the earth wire carries its potential difference.
IT PROVIDES AN ALTERNATE PATH OF LEAST RESISTANCE
Colour of the neutral wire
Blue
Purpose of the neutral wire
Completes the circuit with a potential difference of 0V
Colour of the live wire
Brown
Purpose of the live wire
High potential difference of 230V causing a large current to flow to the appliance
Purpose of the fuse in plugs
Fuse connected to the live wire. If the live wire touches the neutral wire (short circuit) a very large current flows. This causes the fuse to melt causing a large current to flow through if you touched it.
