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Question
Two test tubes with water are heated by a candle flame as shown in Fig. 7.16. Which thermometers (Fig. 7.16a or Fig. 7.16b) will record a higher temperature? Explain.
🔗 Concept: 7.2 Convection
Show Answer
Fig. 7.16(b) records higher temperature — candle heats from below
Explanation
- Fig. 7.16(b): Candle is below.
- Bottom water heats up first.
- Hot water rises by convection → entire tube heated → higher reading.
- Fig. 7.16(a): candle at top → hot water stays at top.
- Cool water at bottom (thermometer) doesn’t circulate → lower reading.
- Convection is effective only when heated from below .
Convection is effective only when heating from below; hot water rises and heats the entire tube.
