To wholly convert a given amount of heat energy into mechanical energy is?

Question

A) possible using an atomic reactor.

B) possible using a steam engine.

C) possible using a simple machine.

D) impossible regardless of the technique used.

Answer 1

Answer D is correct. Just about every heat enging ever constructed is very wasteful of heat and some of them are as low as 10% in thermal efficiency (locomotive steam engine) or can be as high as 75% (steam-turbine), but never 100% or anything close.

One reason is that the gas or steam passing through the engine must escape freely at the exhaust end and if there is some resistance to its flow there it will slow down the operation of the rest of the energy conversion. Some very ingeneous devices have been invented to try to improve on this situation but they are too impractical to be commercially viable and most engines continue to be wasteful of fuel.

Answer 2

D)

It is impossible to perfectly convert one form of energy to another. It violates the second law of Thermodynamics, since according to it any energy transfer must result in an increase of entropy, if you could have a perfect transfer, the entropy would stay the same.

The second law is rather jokingly referred to as the "You can't break even" law.

If your question was possible then perpetual motion machines would be possible to, since they could convert it from heat to mechanical and then back, and do that for forever.

Answer 3

D. Impossible regardless of the technique used.

The maximum efficiency possible would be produced by a heat engine running in the Carnot cycle. That efficiency, in percent, is 100 [T(hot)-T(cold)]/T(hot), where T(hot) and T(cold) are temperatures in Kelvins.