Supply and demand
4 marks · NormalThe table shows the time it takes different types of power stations to start generating electricity after being turned on.
| Type of power station | Time to start generating (hours) |
|---|---|
| Nuclear | 12 |
| Coal-fired | 8 |
| Oil-fired | 4 |
| Gas-fired | 0.5 |
| Hydroelectric | 0.03 |
Which power station is best for meeting a sudden, short-term increase in demand? Explain your answer.
Suggest one reason why nuclear power stations are not used to meet sudden increases in demand.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Hydroelectric, because it starts generating electricity fastest (in 0.03 hours). · must show correct choice and clear linked explanation
(b) Nuclear power stations take many hours to start due to the need to safely start the fission reaction and heat the reactor core; they cannot respond quickly to demand changes. · must show reasons for slow response, linked to nuclear start-up process
Common mistakes: Choosing nuclear for a sudden increase; not explaining reasoning
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Chooses hydroelectric as fastest starter; supported by data.
B1 (a) · 1 mark · Explains in terms of time to start (needs less time than others).
B1 (b) · 1 mark · Gives a valid reason for nuclear not being suitable for sudden demand (e.g., slow/complex start-up, safety).
B1 (b) · 1 mark · Mentions process: starting fission reaction, heating reactor, or safety delays.
Worked solution
a) The hydroelectric station is best, as it can start in 0.03 hours (less than 2 minutes), much faster than others.
b) Nuclear power stations take a long time due to safety procedures for starting the fission reaction and heating up the reactor core.