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GCSE Questions: Energy Sources

Q9. The diagram shows an electric road sign.

(a) The road sign is powered by an electrical generator which has an efficiency of 40%.

Complete the Sankey diagram in the grid belowfor an electrical generator which has an efficiency of 40%.

The input is 10 squares - so a 40% output will be 4 squares (to the right).

That leaves wasted energy of 6 squares (downwards).

correct arrow widths 4 squares and 6 squares

correct labels of useful and wasted energy

[2 marks]

(b) The road sign uses high efficiency LED bulbs. What does high efficiency mean? Tick one box.

  Tick here
the bulbs have a high energy input  
a high proportion of the energy output is useful
a high proportion of the energy output is wasted  

[1 mark]

(c) Some road signs are powered by batteries recharged by solar cells.

In one sign the solar cells have a total power output of 200 W.

Calculate the energy that the solar cells will transfer in 1 hour.

P = E/t

so, energy (in joules) = power (in watts) x time (in seconds)

200 W = 200 J/s

1 hour = 60 minutes = 60 x 60 seconds = 3600 s

energy = 200 x 3600 = 720,000 J

(or 720 kJ)

 

[3 marks]

(d) Some road signs are powered by batteries recharged by both solar cells and wind turbines.

Give two advantages of having both solar cells and wind turbines available to recharge the batteries.

any two from:

greater input

takes less time to charge

energy sources are renewable

can be used in remote location

no carbon dioxide/greenhouse gases released or doesn't contribute to global warming

no fuel / running cost

wind turbine can recharge the batteries at night

when it isn't windy, solar cells can recharge batteries

[2 marks]

(Total 8 marks)