The Action Lab: Boiling water with mechanical energy

The Action Lab:

The energy required to heat 1 kilogram of water (1 liter) from 24 C to 100 C can be calculated by knowing the heat capacity of water in that temperature range. About 4184 Joules per kilogram per °C.

Energy_Joules = (1 kg) * (4184 J/kg°C) * (76°C) = 318,384 Joules

(1 Joule) = (1 Watt) * (1 Second)

If you add energy at 1000 Watts, that would take you ( 318,384 Joules)/(1000 Watts) = 318.384 second = 5 minutes and 18.384 seconds. So heating a liter of water in a 1000 Watt microwave at perfect efficiency takes just about 5 minutes 20 seconds. You can check the effective power of your microwave by measuring the temperature of a known mass of water before and after heating in the microwave for a specific time.

Sir Benjamin Thomson, Count Rumford, demonstrated the connection between mechanical energy and heat when he noticed how much heat was generated when boring a cannon. Later, James Prescott Joule determine the “mechanical equivalent of heat”, the amount of work needed to raise the temperature of a mass of material like water from one temperature to a higher temperature. The unit Joule is named after him.

Richard Collins, The Internet Foundation