It takes 56.5 kilojoules of energy to raise the temperature of 150 milliliters of water from 5 °C to 95 °C. If you use an electric water heater that is 60% efficient, how many kilojoules of electrical energy will the heater actually use by the time the water reaches its final temperature?

Question

Physics

Karina Miranda

9 May, 23:23

It takes 56.5 kilojoules of energy to raise the temperature of 150 milliliters of water from 5 °C to 95 °C. If you use an electric water heater that is 60% efficient, how many kilojoules of electrical energy will the heater actually use by the time the water reaches its final temperature?

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Simpson · Answer 1

If 56.5kJ are needed to raise the temp by 90°C and if the heater is 60% efficient that means that:

60% X y = 56.5kJ

where y is the electrical energy in kJ that the heater will use.

y = 94.2kJ