A car engine is an example of
(a) internal combustion engine
(b) external combustion engine
(c) neither internal nor external combustion engine
(d) both internal and external combustion engine

Hint:In order to solve this question, we need to have the knowledge and concept about the Carnot engine.

Complete answer:
A car engine is an example of an internal combustion engine. Internal-combustion engine, any of a group of devices in which the reactants of combustion (oxidizer and fuel) and the products of combustion serve as the working fluids of the engine. Such an engine gains its energy from heat released during the combustion of the unreacted working fluids, the oxidizer-fuel mixture. This process occurs within the engine and is part of the thermodynamic cycle of the device. Useful work generated by an internal-combustion (IC) engine results from the hot gaseous products of combustion acting on moving surfaces of the engine, such as the face of a piston, a turbine blade, or a nozzle.

Hence, the correct answer to the question is option (a).

Additional Information: Carnot principles are only for the cyclical devices like heat engines, which state that the efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between the same two reservoirs. The efficiencies of all reversible heat engines operating between the same two reservoirs are the same.

Note:While solving this question, we should be aware of the different types of combustion engine. Especially about the Carnot engine. Knowledge of how an engine works in a Carnot cycle and basic concept of it is required to solve this question.