P5 Electricity in the home Flashcards
What is direct current?
Current which flows in one direction
What is alternating current?
Current which can repeatedly reverse its direction of flow
What are the two types of wire in a live circuit?
- Live wire (alternatively positive and negative every cycle)
- Neutral wire (wire at zero volts)
What is the peak potential difference of an alternating current supply?
The maxium voltage measured from zero vaults
How do you measure the frequency of an alternating current supply?
Frequency = 1 / time taken for one cycle
What are socket and plug cases made of?
Stiff plastics that enclose electrical connections as plastic is a good electrical insulator
What is a mains-cable made of?
Two or three insulated copper wires surrounded by an outer layer of flexible plastic material
What is the power supplied to a device?
The energy transferred to it each second
How do you find electrical power supplied to an appliance?
Power = Amps x Voltage
How do you calculate charge flow?
Charge flow = current x time
When charge flows through a resistor…..
energy transferred to the resistor makes it hot
How do you calculate energy transferred to a component?
Energy = potential difference x charge flow
What does a domestic electricity meter measure?
Energy supplied
How do you calculate useful energy used?
Useful energy used = efficiency x energy supplied
Why are pylon cables made of aluminium?
- They are light and highly condusive
- They are less resistant
What are the advantages of overheard cable?
• Relatively cheap to link between tall towers
• Easy access to maintain cables
• Open to air cooling of cables
What are the disadvantages of overheard cable?
• Visually unappealing, (ruin landscapes)
• Vulnerable to the weather
• Must cut across large amount of land
What are disadvantgaes of Underground Power Cables?
- Very expensive to put miles and miles of cable underground
- Maintenance would be harder as you would have to dig them up
- The cables can get hot, hard to cool underground therefore must be thicker
- Would need to clearly mark everywhere they are to reduce the risk of accidentally digging it out
Batteries use…
DC currents (Direct Current)
Plugs use…
AC current (Alternating Current)
What is Direct Current (DC)?
The current flows in one direction only.
- E.g. cells & batteries
What is Alternating Current (AC)?
When the current constantly changes direction
E.g. mains supply, the power socket