Work Step by Step
In an isothermal process, the change in internal energy is zero, and Q = W. In an isothermal compression, 100 J of work can be converted into 100 J of heat. In an isothermal expansion, 100 J of heat is converted into 100 J of work. Choice A is tempting because the second law of thermodynamics says it is impossible to make a 100 percent efficient heat engine. However, the question does not say that we must consider a complete cycle.