Question

The overall efficiency is defined as the ratio of the work obtained at the crankshaft in a given time to the energy supplied during the same time.

(a) True

(b) False

The question was posed to me by my school teacher while I was bunking the class.

The origin of the question is Engine Efficiencies topic in section Measurements and Testing/Performance Parameters and Characteristics of IC Engine

Answer 1

The correct answer is:

(b) False

The definition provided in the question is actually describing mechanical efficiency, not overall efficiency. 

Overall efficiency takes into account the total energy input (including losses due to friction, heat, and other factors) and compares it to the useful work output. It includes both the mechanical and thermal efficiencies of the engine, giving a broader picture of the engine’s performance.