Sure! Here’s a worksheet for Year 7 students to practice calculating energy efficiency:

1. Calculate the energy efficiency of a light bulb that produces 800 lumens of light with an input power of 10 watts.

2. A refrigerator uses 500 watts of power to remove 1000 joules of heat energy from its interior. Calculate its energy efficiency.

3. A car engine produces 2000 joules of useful work while consuming 5000 joules of fuel energy. Determine the energy efficiency of the car engine.

4. A solar panel receives 1000 joules of sunlight energy and converts it into 800 joules of electrical energy. Calculate the energy efficiency of the solar panel.

5. A wind turbine generates 5000 joules of electrical energy from 8000 joules of wind energy. Determine the energy efficiency of the wind turbine.

6. A laptop computer consumes 50 watts of power and produces 40 watts of useful work. Calculate its energy efficiency.

7. A heater converts 2000 joules of electrical energy into 1800 joules of heat energy. Determine the energy efficiency of the heater.

8. A hydroelectric power plant converts 5000 joules of water energy into 4000 joules of electrical energy. Calculate the energy efficiency of the power plant.

9. A microwave oven consumes 1000 watts of power and produces 800 watts of useful heat energy. Determine its energy efficiency.

10. A bicycle dynamo converts 1000 joules of mechanical energy into 800 joules of electrical energy. Calculate the energy efficiency of the dynamo.

Remember to show your calculations and express the energy efficiency as a percentage. Good luck!