i- During one year, 1.25 × 1018 J of energy was transferred from the National Grid.
number of seconds in 1 year = 3.16 × 107
Calculate the mean energy transferred from the National Grid each second.
Give your answer to 3 significant figures.
[2 marks]
SOLUTION
ii- Figure 5 shows a house with a solar power system.
The solar cells generate electricity.
When the electricity generated by the solar cells is not needed, the energy is stored in a large battery.
ii- The charge flow through the cable between the solar cells and the battery in 24 hours was 27 000 coulombs.
Calculate the mean current in the cable.
[4 marks]
SOLUTION
Use the formula of current.
iii- At one time, the total power input to the solar cells was 7.8 kW.
The efficiency of the solar cells was 0.15.
Calculate the useful power output of the solar cells.
[3 marks]
SOLUTION
Don’t forget to convert KW into W. you take the helo from the following table.
iv- It is unlikely that all of the electricity that the UK needs can be generated by solar power systems.
Explain why.
[2 marks]
SOLUTION
A large area is required for all solar panels to be installed due to their very low efficiency (0.15 as provided in the question).
