Efficiency of Energy Transfer

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A series of free GCSE/IGCSE Physics Notes and Lessons.

Efficiency of Energy Transfer

The following diagram gives the formula for energy efficiency. Scroll down the page for more examples and solutions on how to use the formula.
Energy Efficiency

In this lesson, we will

  • Describe what is meant by efficiency of energy transfer.
  • How to calculate energy efficiency.
  • Describe ways to increase the efficiency of energy transfer.


  1. An electric hob is used to heat water. 15,000 J of thermal energy is transferred by the hob. 12,000 J of thermal energy passes into the water. Calculate the efficiency of energy transfer into the water.
  2. An electric current delivers a power of 60 watts to a light bulb. 3 watts of electrical energy are transferred to light energy. Calculate the efficiency of the bulb.

GCSE Physics - Efficiency

  • The idea that devices aren’t 100% efficient
  • What efficiency is
  • The equation for efficiency
  • Examples of how to calculate efficiency
  • Why some devices like electric heaters are sometimes considered to be 100% efficient

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.
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