Convection of heat:
Convection is the transfer of heat from one place to another through the movement of liquids or gases. When a liquid or gas is heated, it becomes lighter and rises upward. The cooler, heavier liquid or gas moves down to take its place. This continuous movement forms convection currents that transfer heat.
Examples of Convection
- Boiling Water
- Hot Air Balloon
Activity:
Experimental setup
Two identical paper cups are suspended upside down from the two ends of a wooden stick using threads of equal length. The cups are adjusted so that the stick remains horizontal. A burning candle is then placed below one cup, and the movement of the cups is observed.
Observation
You observed that the cup under which the candle was placed, rises up.
Result
The air around the candle flame heats up. As the air in the cup warms up, it expands and occupies more space. As a result, it becomes lighter and rises up.
Air expands when heated. This can be observed by placing a partially inflated balloon in sunlight; as the air inside warms, it expands and the balloon becomes larger.
Similarly, when an incense stick burns, it produces smoke containing hot gases and tiny solid particles. Since the smoke is warmer than the surrounding air, it rises upward. This demonstrates the movement of heated air associated with convection.
Heating of air and rising of warm air
