Question

In the following figure, assuming the two thermometers have the same initial reading, which of the two would record a higher rise in temperature, when placed near the candle as shown?

• A. A
• B. B
• C. Both A and B would have the same rise in temperature.
• D. The mercury level in A and B would not rise at all.

Answer 1

The correct option is A A

The heat from the candle is transferred to the thermometer A, due to convection. The hot air rises from the flame would heat up the mercury bulb which in turn expands the mercury.
The heat from the candle is transferred to the thermometer B, due to radiation. The heat radiating from the flame would heat up the mercury bulb which in turn expands the mercury.
Out of the two cases, radiation is a less efficient way of heat transfer, as it is slower. Convection currents in A are faster and more effective in transferring the heat. So, the thermometer A would show a higher rise in temperature than B.