[Part 2]- P5- Domestic electricity 🔌 Flashcards
1
Q
What is the national grid ?
Hint: link, power stations
A
- the national grid, consists of a system of transformers and high-voltage cables, that link power stations to consumers.
2
Q
Explain how potential difference is changed by a transformer. [3]
A
- the electricity passes through step-up transformers, which increases the potential difference to several hundred thousand volts, reducing energy loss in the transmission cables.
- then, the electricity passes through step-down transformers- which reduce the potential difference to 230V and this is then passed onto homes.
- If step-down transformers aren’t used, the voltage would be too high for domestic purposes
3
Q
Why is the national grid an efficient way of transferring energy ? [5]
Hint: energy is lost
A
- the national grid is an efficient way of transferring energy because:
- to transmit the huge amount of power needed, you need a high potential difference or a high current.
- ; this is a problem with a high current, since loads of energy is lost because the wires heat up, transferring energy to the thermal energy store of the surroundings.
- So instead, it’s less expensive to increase the potential difference [to about 400,000 V] and then keep the current as low as possible.
- and for a given power, increasing the potential difference, decreases the current= decreases the energy oxide by heating the wires and the surroundings.
4
Q
How can you calculate the potential difference across a primary coil ?
A
- voltage across primary coil ✖️ current in primary coil (A)= voltage across secondary coil ✖️current in secondary coil (A).
- In other terms:
- Vp Ip = Vs Is
5
Q
What are primary and secondary coils ?
Hint: turns
A
- transformers all have two coils- a primary and secondary coil, joined with an iron core.
- step- up transformers have more turns on the secondary coil, than the primary coil.
- and step-down transformers have more turns on the primary coil, than the secondary.
