No Longer On Exam Flashcards
Is main electricity an a.c. supply or a d.c. supply? What do each of these stand for?
Mains electricity is an a.c supply.
a. c.: alternating current.
d. c.: direct current.
Define alternating current and direct current
Alternating current - current that continuously changes direction at a specific frequency.
Direct current - one directional current flow.
What is the frequency and voltage of the UK mains electricity supply?
- Frequency: 50Hz.
- Voltage: 230V.
How many wires are usually in the cables connecting electrical appliances to the mains? Name these wires
- Live wire.
- Neutral wire.
- Earth wire.
State the insulation color used on the earth wire
Green and yellow stripes.
State the insulation color used on the live wire
Brown.
State the insulation color used on the neutral wire
Blue.
Explain when the earth wire does and doesn’t carry a current
- Under normal circumstances, no current flows through the earth wire.
- If a fault occurs in the appliance such as the casing becoming live, current will flow to the ground through the earth wire.
What is the potential difference is the neutral wire at?
0 volts.
State the potential difference between the live and earth wires
230 volts.
What is the purpose of the neutral wire?
To complete the circuit by connecting the appliance back to the mains supply.
For metal appliances, where is the earth wire connected to? Why?
- Earth wire is connected to the metal casing of the appliance.
- If live wire becomes loose and touches the metal casing, the current will flow through the earth wire, preventing electrocution.
What is the purpose of the fuse?
An electrical component that protects circuits and electrical components by melting when the current becomes too high. This breaks the circuit, disconnecting it all.
