Question

Based on the second law of thermodynamics why must a machine always be less than 100% efficient?

A.Heat never moves from cold to hot.
B.Heat is never converted completely into mechanical energy.
C.Heat never flows from hot to cold.
D.Entropy never increases.

Answer 1

B

Step-by-step explanation:

Use logic

Answer 2

Answer: B.Heat is never converted completely into mechanical energy.

Step-by-step explanation:

According to the second principle of thermodynamics:

"The amount of entropy in the universe tends to increase over time"

However the first formulation of this law (by Sadi Carnot) states:

"There is an upper limit to the efficiency of conversion of heat to work, in a heat engine "

This means the heat cannot be completely transformed into mechanical energy in a machine. That is why a machine's effieciency is always less than 100%