Automobile engines work on the principle of:
thermal expansion of solids
thermal expansion of liquids
thermal expansion of gases
The correct option is D thermal expansion of gases
Thermal expansion involves change in volume of an object when it is heated. The combustion of fuel in an automobile engine produces gas at high pressure. That pressurized gas is expanded in a chamber to drive a piston which in turn rotates the crank. Thus automobile engines work on the principle of thermal expansion of gas.