National grid

Question 1

What is a national grid

Answer 1

The national grid is a gaint system of cables and transformers that covers the UK which connects power stations to consumers

Question 2

What does the national grid transfer

Answer 2

Electrical power from power stations anywhere on the grid to anywhere else on the grid where its needed e.g. home

Question 3

Throughout the day, demand..

Answer 3

Changes. Power stations have to produce enough electricity for everyone to have it when they need it

Question 4

Prediction of when most electricity is used

Answer 4

Demand increases when people get up in morning, come home from school or work when it gets colder or darker.
Popular events like sporting final shown on TV causes a peak in demand

Question 5

How do power stations keep up with the demand?

Answer 5

They usually run below their maximum power output so there’s spare capacity to cope with high demand even if there’s an unexpected shut down of anothet station.

Lots of smaller power stations that start up quickly are also kept in standby just incase

Question 6

What makes the national grid an effecicent way of transferring energy? P=VI

Answer 6

To transmig hugr amount of power needrf, you need either high PD or high current. High current = lose loads of energy as wire heats uo and energy lost to TES of surrounding

Its cheaper to boost PD up really high (400 000 V) and keep current low as possible.

for every given power, increasing PD decreases current and decreases energy losy by heating to wires and surrounding.

Question 7

To get the PD to 400,000 wV for efficient transmission we use..

Answer 7

Transformers which have 2 coils, a primary coil and secondary coil joined with an iron core.

Question 8

How is PD increased?

Answer 8

Using step up transformer. they have more turns on secondary coil than primary coil. As pd increased by transformer, current is decreased.

Question 9

When is the PD reduced again?

Answer 9

At local consumer using step down transformer. More in turns on primary coil than secondary coil.

Question 10

Transformers are 100% efficient so

Answer 10

Power in primary coil = power in secondarg coil

Question 11

Formula

Answer 11

Pd across Primary coil (V) X current in Primary coil (A) = Pd across secondary coil (V) X current in secondary coil