Question

A carnot engine extracts 1200J of energy from a hot reservoir. What is the amount of work done by it? Temperatures of hot and cold reservoirs are 200K and 150K respectively.

(a) 800J

(b) 900J

(c) 600J

(d) 850J

This question was addressed to me during an online interview.

The origin of the question is Thermodynamics topic in section Thermodynamics of Physics – Class 11

Answer 1

The correct option is (b) 900J

For explanation: The efficiency of a carnot engine is:

1- T2/T1 = 1-150/200 = 1/4.

Efficiency is also given by: 1 – Q2/Q1 = 1 – Q2/1200 = 1/4.

Q2 = 3/4 *1200 = 900J.