Safe electricals Flashcards
1
Q
What device changes resistance?
A
A variable resistor, or rheostat changes the resistance. Longer lengths of wire have more resistance; thinner wires have more resistance.
2
Q
Voltage
A
- Voltage (potential difference) is measured in volts (V) using a voltmeter connected in parallel.
- For a fixed resistor, as the voltage across it increases, the current increases.
- For a fixed power supply, as resistance increases, the current decreases.
3
Q
Resistance Eq.
A
resistance = voltage/current
4
Q
Voltage Eq.
A
voltage = resistance x current
5
Q
Current Eq.
A
current = voltage/resistance
6
Q
All types of wires
A
- The live wire carries a high voltage around the house.
- The neutral wire completes the circuit, providing a returns path for the current.
- The earth wire is connected to the case of an appliance to prevent it becoming live.
7
Q
Double insulated
A
Double insulated appliances do not need an earth wire as the outer case is not a conductor.
8
Q
What does a fuse contain?
A
- A fuse contains wire which melts, breaking the circuit, if the current becomes too large.
- No current can flow, preventing overheating and further damage to the appliance.
- A re-settable fuse (circuit-breaker) doesn’t need to be replaced to restore power; it can be re-set.
9
Q
What does the earth wire and fuse stop?
A
- Earth wires and fuses stop a person receiving an electric shock if they touch a faulty appliance.
- As soon as the case becomes ‘live’, a large current Flows In the Earth and live wires and the fuse ‘blows’.
10
Q
Power Eq.
A
power = voltage x current
