Efficiency & Energy Resources Practice Questions

Complete the table by writing renewable or non-renewable for each energy resource.

Calculate the efficiency of the food mixer.

Give your answer as a percentage.

efficiency = .............................................................. %

Name one way in which energy is wasted by the food mixer.

State the effect on the rate of cooling of the house of making the external walls thicker.

The builder chooses a wall material with a low thermal conductivity.

Explain how this reduces the rate of cooling of the house.

Explain why the conveyor belt system is less efficient when the bearings become hot.

An engineer applies oil to the bearings of the rollers.

Explain how the oil increases the efficiency of the conveyor belt.

During one journey, $250\,000\ \mathrm{J}$ of energy is supplied to the motor.

Calculate the useful energy transferred by the motor during this journey.

useful energy transferred = .............................................................. J

Suggest and explain one change that could be made to increase the efficiency of the lift.

Describe the changes in the use of energy resources shown in the table.

Explain two reasons for the trends shown in the table.

Give one disadvantage of generating a large fraction of a country's electricity from wind, and explain the problem this causes.

State the independent variable in this investigation.

State which material is the best insulator. Use data from the table to support your answer.

Give two improvements the student could make to her method so that her conclusion is more valid.

Name the useful energy transfer that takes place when the scooter is moving, and name two ways in which energy is wasted.

Explain why the energy that is wasted by the scooter cannot be used again to drive the scooter.

Calculate the overall efficiency of the gearbox and generator together.

Give your answer as a percentage.

overall efficiency = .............................................................. %

In one minute, the blades transfer $6.0 \times 10^{6}\ \mathrm{J}$ of energy to the gearbox.

Calculate the useful electrical energy produced by the generator in this minute.

useful electrical energy = .............................................................. J

Explain what happens to the energy that is not transferred usefully by the gearbox, and suggest how the efficiency of the gearbox could be increased.

Compare the use of natural gas and wind as energy resources for generating electricity.

In your answer you should consider the reliability, the environmental effects and the availability of each resource.