# Condition for irreversible heat transfer process - Thermodynamics

**Q. Heat transfer is an irreversible process if***- Published on 20 Aug 15***a.** the temperature difference between the two bodies is infinitesimally small

**b.** the temperature difference between the two bodies is finite

**c.** both a. and b.

**d.** none of the above

**ANSWER: the temperature difference between the two bodies is finite **

If the temperature difference between the two bodies approaches zero, the heat transfer process approaches irreversibility. In a reversible heat transfer process the temperature difference is infinitely small. But to transfer a finite amount of heat through an infinitesimal temperature difference, we need infinite time or infinite area. But this is not possible. Actual heat transfer process takes place through an finite temperature difference and these are irreversible.