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True or false? Mains supply electricity is an alternating current
True
What is the potential difference and frequency of the UK mains supply?
230V
50 cycles per second (50Hz)
Name and give the colours of the 3 wires in a three-core cable
Neutral Wire - Blue
Live Wire - Brown
Earth Wire - Green and Yellow
Give the potential differences for the three wires in a three-core cable
Neutral Wire - 0V
Live Wire - 230V
Earth Wire - 0V
Explain why touching a live wire in dangerous
Your body is at 0V normally
If you touch the live wire, a large potential difference is produced and current flows through you
Large electric shocks like this can injure or kill you
State 3 equations that can be used to calculate electrical power.
Energy Transferred (I) = Power (W) x Time (s) [E=Pt]
Power (W) = Potential Difference (V) x Current (A) [P=VI]
Power (W) = Current² (A) x Resistance (Ω) [P=I²R]
What is the power rating of an appliance?
The maximum safe power that they can operate at
Explain why electricity is transferred by the national grid at a high pd but low current
To reduce the amount of energy lost (as wires heat up)
What are the functions of step-up and step-down transformers?
To increase and decrease the potential difference
Note
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