Mains Electricity Flashcards
What is direct current?
- Current flows from positive to negative in one direction.
Give a source of direct current.
- Cell.
Can direct current have a negative voltage/ current?
- Yes.
- Must stay negative though.
What is alternating current?
- Current changes direction
Give an alternating current source.
- Mains Electricity.
How do we calculate the voltage of a power supply using AC graph?
- Read off peak voltage.
What is meant by frequency?
- Frequency is how many cycles an electron completes each second.
What is the voltage of mains electricity?
- 230V
For every coloumb of charge, it transfers 230J
How many times does the current change direction in the mains supply each second ?
- 50
- 50Hz = frequency
What 3 wires is a 3- pin plug made up of?
- Live wire: brown
- Neutral Wire: blue
- Earth Wire: Green
What is the live wire?
- Part that carries current to device
- Has voltage of 230V.
What is the Earth wire?
- Safety
- Connected to outer casing of device
- If device becomes live from high current/ live wire is near device, carries current to ground.
- Directs current away from device
What does the Earth wire avoid?
- Avoids electric shocks.
What does the neutral wire do?
- Completes the circuit.
- Has no voltage.
What are the actual wires made of?
Why?
- Copper
- Good condudctors
Describe what is meant by double insulation.
- Electric components are coated in plastic and covered by plastic casing.
Do double insulated devices need an Earth wire?
- No.
- Because the outer casing CAN’T become live (insulated)
- (Electrical components covered and outer case isn’t metal.)
What does the fuse protect?
- The fuse protects the device.
How do I work out frequency?
1/ time period
time period of one wave = from trough to trough// peak to peak.
What is meant by direct potential difference?
- Potential difference is in once direction.
What is meant by alternating potential difference?
- Potential difference is changing direction.
What are the dangers of providing connection between live wire and the earth?
- You will be earthed
- You will recieve electric shock.
What is the potential difference between The Earth and the live wire?
- Live wire = 230V
- Earth wire = 0V
- Difference = 230V
What is the potential difference of the neutral wire?
- The neutral wire is at, or close to, earth potential (0V)
What is the potential difference of The Earth Wire?
- 0V
- It only carries a current if there is a fault.
True or False
If the switch in mains electricity is closed, can a live wire still be dangerous.
- Yes. Live wire can still be dangerous if switch is closed.
