# Efficiency of Energy Transfer

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### 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.

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.

Examples:

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

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