# Efficiency calculations involving energy

## Stage 1

1. A light bulb produces 77.07 J of light energy when it is supplied with 367 J. Calculate the efficiency of the light bulb.

2. An electric heater produces 158.92 J of heat energy when it is supplied with 274 J. Calculate the efficiency of the heater.

3. An electric motor raises an object. The motor is supplied with 335 J of energy and the object's gravitational potential energy store increases by 107.2 J. Calculate the percentage efficiency of the motor.

4. A kettle is supplied with 317 J of energy and produces 41.21 J of heat energy. Calculate the percentage efficiency of the kettle.

5. A toaster produces 83.46 J of heat energy when it is supplied with 321 J. Calculate the percentage efficiency of the toaster.

## Stage 2

6. A kettle is 59% efficient. If the kettle outputs 28.32 J of useful energy, calculate the total energy supplied to the kettle.

7. A toaster has an efficiency of 0.36. If the toaster outputs 33.84 J of useful energy, calculate the total energy supplied to the toaster.

8. A kettle is 16% efficient when it is supplied with 72 J. Calculate the useful energy output by the kettle.

9. An electric heater outputs 274.45 J of useful energy. The heater has an efficiency of 0.55. Calculate the total energy supplied to the heater.

10. An electric motor raises an object and is supplied with 75 J. The motor is 22% efficient. Calculate the useful energy output by the motor.

## Stage 3

11. An electric heater is 12% efficient when it is supplied with 55 J. Calculate the useful energy output by the heater.

12. A kettle is supplied with 441 J and is 38% efficient. Calculate the useful energy output by the kettle.

13. A light bulb is supplied with 10 kJ and has an efficiency of 0.15. Calculate the useful energy output by the light bulb.

14. A light bulb outputs 81.6 J of useful energy. The bulb has an efficiency of 0.24. Calculate the total energy supplied to the light bulb.

15. An electric motor raises an object. The motor is supplied with 486 kJ of energy and the object's gravitational potential energy store increases by 68.04 kJ. Calculate the efficiency of the motor.

1. 0.21

2. 0.58

3. 32 %

4. 13 %

5. 26 %

6. 48 J

7. 94 J

8. 11.52 J

9. 499 J

10. 16.5 J

11. 6.6 J

12. 167.58 J

13. 1.5 kJ

14. 340 J

15. 0.14