A heat engine is 20% efficient. If it loses 800 J to the cooling system and exhaust during each cycle, the work done by the engine is:

A. 200 J

B. 1000 J

C. 800 J

D. 20 J

Answer: A. 200J

Therefore, the workdone by the heat engine is 200J

Explanation:

Given;

The efficiency of the heat engine is E = 20% = 0.2

Heat loss L = 800J

For an heat engine the efficiency is measured by the amount of workdone by the heat engine when compared to the heat generated.

Efficiency E = workdone/heat generated * 100%

Heat generated G = workdone W + heat loss L

G = W + L

According to the question.

W = 20% of G

W = 0.2G ... 1

L = 80% of G

L = 0.8G

G = L/0.8 ... 2

Substituting equation 2 to 1

W = 0.2 (L/0.8)

And L = 800J

W = 0.2 (800/0.8)

W = 200J

Therefore, the workdone by the heat engine is 200J