A cooling system or a radiator in a motor car works on the principle of convection. The engine in a motor car produces a lot of heat due to the combustion of fuel. This heat needs to be dissipated to prevent the engine from overheating and malfunctioning. The cooling system consists of a radiator, which is usually located at the front of the car.

The hot coolant from the engine enters the radiator, which is made up of many small tubes. The radiator has thin fins attached to these tubes, which provide a large surface area for the transfer of heat. As the hot coolant passes through the tubes, it releases heat to the surrounding fins. At the same time, the air that flows through the radiator absorbs this heat and becomes hot. The hot air rises, and cooler air from outside the car is drawn in to replace it, creating a convection current. This process continues, and the coolant becomes cooler as it passes through the radiator.

Thus, the principle of convection is used to transfer heat from the hot coolant to the surrounding air, and thereby cool the engine.