When you transform energy what is lost?

Answer 1

There is usually some heat lost. For example you boil a kettle of water, you know the input heat from the rating of the kettle in Kw and the time taken, and if you measure the amount of water boiled and its initial temperature you can work out the heat given to the water. But there will also be some heat lost from the outside of the kettle to the room where it is.

In a power plant using the Rankine cycle, as much heat as possible is obtained from the steam in the turbine, but even when the back end runs at a vacuum to increase efficiency, a large amount of heat at low temperature is rejected to the condenser cooling water, and this is too low in temperature to be useful, it is just lost to the environment.

In an internal combustion engine, chemical energy is converted to heat which then does mechanical work, but as you must have noticed, a lot of heat is rejected into the radiator and into the exhaust.

Answer 2

Energy conversions are quite inefficient. Some of the initial energy is always "Lost" to the environment as heat. (it is not really lost because energy cannot be created or destroyed, but that a portion given off as heat is least partly unusable)

Answer 3

Some useful energy is usually converted into unusable energy, so you might state any of the following:

• Useful energy is lost
• Unusable energy increases
• Entropy increases

Answer 4

When energy is transformed, some of it is lost as heat due to inefficiencies in the conversion process. This is known as thermal energy or waste heat. It is a result of the second law of thermodynamics, which states that not all the input energy can be converted into usable output energy.