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Take a sheet of paper and draw a spiral on it, as shown in Fig. 7.17a. Cut the paper along the spiral. Suspend the cut spiral above a burning candle, as shown in Fig. 7.17b. Observe what happens and provide an explanation for your observation.
Show Answer
The paper spiral rotates, because hot air rising from the candle pushes it.
Key Points
- The candle heats the air around its flame.
- Warm air is lighter, so it rises upward.
- This rising warm air is a convection current.
- The moving air pushes against the paper spiral.
- The spiral spins as the warm air rises through it.
- This shows convection — heat transfer by the movement of air.
Rising warm air (convection) spins the paper spiral above the candle.
