Pupil sheet · Energy resources
Energy resources — return questions
Name ______________________ Date ____________
Use one to two weeks after the lessons. Keep the notes and the lesson closed.
1. state / describe
A power station burns wood pellets made from fast-growing trees. (a) State the type of energy resource that wood pellets are. (b) Describe how this power station’s way of generating electricity is different from a coal-fired power station’s, if it is different at all. (c) Supplement. Describe how the energy in the wood pellets came from the Sun, starting with the process that releases energy in the Sun.
(a) Type of resource
(b) Different from coal?
(c) Supplement: From the Sun
2. describe / explain
A hospital in a sunny town wants to rely less on electricity from a coal-fired power station. It fits solar cells on its roof and keeps a diesel generator for emergencies. (a) Describe one advantage of the solar cells, in terms of renewability or environmental impact. (b) Describe one disadvantage of the solar cells, in terms of reliability. (c) Explain why the hospital must keep a backup such as the diesel generator. (d) The solar cells on the roof give at most 50 kW, but the hospital needs up to 400 kW. Describe this disadvantage, using the word scale.
(a) Advantage
(b) Disadvantage: reliability
(c) Why keep a backup
(d) Scale
3. state / explain / suggest
A phone charger feels warm while it charges a phone. (a) State the useful energy output of the charger. (b) Explain why the charger gets warm, using the idea of efficiency. (c) A friend says the warmth shows that energy is being destroyed. Explain why this is wrong. (d) A new charger charges the phone just as quickly but stays cooler. Suggest what this tells you about its efficiency.
(a) Useful energy output
(b) Why it gets warm
(c) What is wrong
(d) The new charger
4. calculate
(a) In one turbine of a tidal barrage, for every 500 kJ that the moving water gives the blades, the turbine passes 470 kJ to the generator, and the generator gives 440 kJ of electrical energy. Calculate the efficiency of the generator alone. (b) An electric motor in a lift takes in 12 kW of electrical power and gives a useful power output of 7800 W. Calculate its efficiency. Give your answer to 2 significant figures.
(a) Efficiency of the generator: ______________ unit ________
(b) Efficiency of the motor: ______________ unit ________