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GCSE Questions: Energy Sources

Q19. An electric car has a motor that is powered by a battery.

A diesel car has an engine that is powered by diesel fuel.

(a) The table compares an electric car and a diesel car.

Power source Energy density in MJ / kg Mass of power source in kg Total mass of car in kg Time to recharge battery or refill fuel tank in minutes
Battery 0.95 280 1600 40
Diesel fuel 45 51 1500 3

 

The electric car has a range of 400 km with a fully charged battery.

The diesel car has a range of 1120 km with a full tank of diesel.

(i) Explain the difference in the time needed to complete a 500 km journey using the electric car compared with the diesel car. Assume both cars travel at the same speed.

The electric car journey will take a longer time because the battery will need recharging so the car will need to stop for 40 minutes to recharge.

[2 marks]

(ii) Energy density is the amount of energy stored per kilogram of the energy source.

Use data from the table to show why the diesel car has a greater range than the electric car.

Assume the efficiency of the two cars is the same. Include calculations in your answer.

Energy stored in diesel = 45 × 51 = 2295 (MJ)

Energy stored in batteries = 0.95 × 280 = 266 (MJ)

So the diesel stores more energy than the battery and that is why the diesel car has a higher range.

[3 marks]

(b) Engineers have developed a way of charging electric cars while they are driving along the road. Coils of wire buried under the road transfer energy to the car's battery as the car is passing over the coils. The photo shows a charging lane on a motorway.

Suggest two advantages of using this method to charge electric cars compared with plugging them into the mains electricity supply.

Any two from:

recharging is a continuous process so cars do not need to stop to recharge which makes shorter journey times, as they don't have to wait for battery to recharge. It results in a longer time between recharges and the range of the electric car is increased.

fewer cells needed in the car so a smaller battery needed in the car

more cars can be charged at the same time or fewer charging stations needed.

It is quicker OR reduced cost of charging OR talk of methods of electricity generation - all got you no marks.

[2 marks]

(c) When electric cars are not being driven, energy stored in their batteries could be used to meet sudden peaks in electricity demand. Suggest how.

When cars are plugged in the energy from car batteries could be transferred back to the National Grid.

OR energy from car batteries could be used to power household appliances.

 

[2 marks]

(Total 9 marks)