Which of the following is considered as wasted energy in an internal combustion engine?

Heat energy is considered wasted energy in an internal combustion engine because a significant portion of fuel energy is converted into heat rather than useful work. When gasoline or diesel fuel is burned, not all of the energy released is utilized to power the vehicle; much of it escapes into the environment as wasted heat. This heat can result from combustion processes and friction within the engine components.

Although heat energy is a byproduct of the engine operation, engineers strive to improve the thermal efficiency of engines to minimize the amount of energy wasted. In contrast, noise energy, kinetic energy, and mechanical energy are generally not classified as wasted energy in the same way. Noise energy is an unintended consequence of operation, kinetic energy helps in vehicle movement, and mechanical energy represents the useful work being done by the engine. Therefore, heat energy is the correct choice as it embodies the lost potential for work that could otherwise be harnessed.