Question

According to the second law of thermodynamics,

A. Heat energy cannot be completely converted to work
B. Work cannot be completely converted to heat energy
C. For all cyclic processes, we have (dQ/T < 0)
D. The reason all heat engine efficiencies are less than 100% is friction, which is unavoidable.

Answer 1

The second law of thermodynamics states that heat energy cannot be completely converted to work in cyclical processes. Heat engine efficiencies are limited by this law and friction in practical systems.

Step-by-step explanation:

The second law of thermodynamics states that it is impossible in any system for heat transfer from a reservoir to completely convert to work in a cyclical process in which the system returns to its initial state. This means that heat energy cannot be completely converted to work. Most heat engines, such as reciprocating piston engines and rotating turbines, use cyclical processes and are limited by the second law of thermodynamics. The reason all heat engine efficiencies are less than 100% is due to the presence of friction, which is unavoidable in practical systems.