2.14 National Grid

Question 1

What is the national grid? (2)

Answer 1

• A giant web of wires and transformers that covers the UK and connects power stations to consumers (anyone who is using the electricity).
• The national grid transfers energy electrically from power stations anywhere on the grid (the supply) to anywhere else on the grid where it’s needed (the demand) - e.g. homes and industry

Question 2

What are transformers used for?

Answer 2

Transformers are used to increase the generated electricity to a very high potential difference before it is transmitted through the network of the national grid. Transferring electrical power at a very high p.d. helps to reduce energy losses. The p.d. is then reduced by another transformer to a level that is safe for use before being supplied to homes and businesses

Question 3

How do power stations work?

Answer 3

Whether you’re burning fossil fuels or doing nuclear fission, power stations work by generating loads of heat and then converting that thermal energy into electrical energy.

Question 4

What does the amount of electrical energy generated depend on?

Answer 4

It depends on demand. Generally, electricity demand peaks in the afternoon and evening when everyone gets home from work/school and starts cooking and watching TV

Question 5

How do power stations cope with these surges of demand in the evening?

Answer 5

Power stations have lots of spare capacity and so they often run at well below the maximum power output

Question 6

What is the power equation for the national grid?

Answer 6

Power = Voltage X Current
P = V X I

Question 7

What is the problem with having a high current running through the wire in the national grid?

Answer 7

A high current running generates lots of heat because of the resistance in the wire and so it loses loads of energy to the surroundings. This would be rubbish as we are trying to transfer this energy to the whole of the country

Question 8

The national grid has to transmit huge amounts of power, however we keep the current low as having a high current would result in us losing energy. How do we combat this?

Answer 8

We use a very high voltage - this means that once the electricity is generated in the power station we have to increase the voltage before sending it across the country. For that, we use step-up transformers

Question 9

What do step-up transformers do?

Answer 9

Increases the voltage to around 400,000V and decreases the current

Question 10

What do the wires in the national grid do?

Answer 10

The wires transmit the energy all across the country between massive pylons

Question 11

What is used to reduce the voltage in the national grid before it reaches towns?

Answer 11

Step-down transformer

Question 12

What voltage do step-down transformers reduce the voltage back down to?

Answer 12

230V

Question 13

Why is it important we use step-down transformers in the national grid before the energy reaches towns?

Answer 13

It would be extremely dangerous and blow up appliances

Question 14

Fossil fuels and nuclear power stations work by generating thermal energy. Describe how the thermal energy can be turned into electrical energy

Answer 14

The thermal energy generated by the fossil fuels and nuclear power stations can be used to turn water into steam which can then rise and turn turbines. The kinetic energy of the moving turbines can be converted to electrical energy, which is finally sent out across the national grid