Y7 Energy efficiency calculations

• 100%

• 80%

• 40%

• 10%

• 100%

• 80%

• 40%

• 20%

• 100%

• 10%

• 40%

• 20%

What is the efficiency of the machine if the input is 263 J and the output is 142 J? 

• 6.26%
• 54%
• 100%
• 260%

What percent energy is wasted by a machine if the energy input is 262 J and the energy output is 131 J?

• 5%

• 50%

• 100 J

Leaving lights on in vacant rooms, washing clothes in hot water, and driving alone are examples of what?

• low energy efficiency
• moderate energy efficiency
• high energy efficiency

A washing machine uses 250J of electrical energy to produce 125J of useful energy. How efficient is it?

• 5%

• 50%

• 55%

• 100%

Calculate the efficiency of a light bulb if the energy input is 125J but the useful energy output is 25J

• 20%

• 100%

• 50%

• 75%