Heat engine having thermal efficiency of 100% is called as Perpetual Motion Machine of _______.

Heat engine having thermal efficiency of 100% is called as Perpetual Motion Machine of _______.

a. the first kind (PMM1)
b. the second kind (PMM2)
c. the third kind (PMM3)
d. all kinds

Correct Answer : b. the second kind (PMM2)

Explanation :

A Perpetual Motion Machine is a hypothetical machine which can do work indefinitely without an energy source. Heat engine with 100% thermal efficiency obeys the first law of thermodynamics which is law of conservation of energy but it violates the Kelvin-planck statement of second law of thermodynamics. Thus heat engine with 100% thermal efficiency is a PMM2.