# Efficiency calculations involving energy

## Stage 1

1. An electric motor raises an object. The motor is supplied with 22 J of energy and the object's gravitational potential energy store increases by 17.82 J. Calculate the percentage efficiency of the motor.

2. A toaster is supplied with 227 J of energy and produces 59.02 J of heat energy. Calculate the efficiency of the toaster.

3. A light bulb produces 13.68 J of light energy when it is supplied with 38 J. Calculate the percentage efficiency of the light bulb.

4. A kettle produces 57.75 J of heat energy when it is supplied with 165 J. Calculate the efficiency of the kettle.

5. An electric heater is supplied with 370 J of energy and produces 25.9 J of heat energy. Calculate the efficiency of the heater.

## Stage 2

6. A light bulb is supplied with 89 J and is 36% efficient. Calculate the useful energy output by the light bulb.

7. A kettle outputs 270 J of useful energy. The kettle has an efficiency of 0.54. Calculate the total energy supplied to the kettle.

8. A light bulb has an efficiency of 0.6. If the bulb outputs 15 J of useful energy, calculate the total energy supplied to the light bulb.

9. A toaster is supplied with 219 J and has an efficiency of 0.34. Calculate the useful energy output by the toaster.

10. An electric heater has an efficiency of 0.52 when it is supplied with 82 J. Calculate the useful energy output by the heater.

## Stage 3

11. An electric heater outputs 98.12 kJ of useful energy. The heater has an efficiency of 0.22. Calculate the total energy supplied to the heater.

12. A light bulb is 27% efficient. If the bulb outputs 129.33 J of useful energy, calculate the total energy supplied to the light bulb.

13. A toaster is supplied with 252 J of energy and produces 105.84 J of heat energy. Calculate the efficiency of the toaster.

14. A toaster is supplied with 276 kJ and is 26% efficient. Calculate the useful energy output by the toaster.

15. An electric heater is 24% efficient when it is supplied with 83 J. Calculate the useful energy output by the heater.

1. 81 %

2. 0.26

3. 36 %

4. 0.35

5. 0.07

6. 32.04 J

7. 500 J

8. 25 J

9. 74.46 J

10. 42.64 J

11. 446 kJ

12. 479 J

13. 0.42

14. 71.76 kJ

15. 19.92 J