What is the principle behind internal combustion engines?

The principle behind internal combustion engines is centered on the burning of fuel within the engine itself, which produces power. In this type of engine, a mixture of fuel and air is ignited in a confined space, creating a controlled explosion that pushes the engine’s pistons. This process converts the chemical energy stored in the fuel into mechanical energy, which can then be harnessed to perform work, such as turning the wheels of a vehicle.

In contrast, the other options describe different energy sources or mechanisms that do not apply to internal combustion engines. Electricity as a power source pertains primarily to electric motors, while solar energy refers to the harnessing of sunlight through solar panels, which is fundamentally different from the combustion process. Moreover, using compressed air is a principle found in pneumatic systems, which operate on different mechanics than internal combustion engines. Thus, the explanation provided emphasizes that burning fuel inside the engine is the specific process that drives internal combustion engines.