A laboratory thermometer A is kept 7 cm away on the side of the flame while a similar thermometer B is kept 7 cm above the flame of a candle as shown in figure. Which of the thermometers A or S will show a greater rise in temperature? Give reason for your answer.
heat rises.
(as the gas (air) heats up from the flame it expands losing density so it rises :)
the answer is B because hot air will only rise up because of convection
Thermometers B will show a greater rise in temperature because hot air rises up from candle which burns due to convection.
To determine which thermometer, A or B, will show a greater rise in temperature, we need to consider a few factors.
First, let's understand how heat is transferred. In this case, the heat from the flame of the candle will be transferred to the thermometers through three main methods: conduction, convection, and radiation.
1. Conduction: This is the transfer of heat through direct contact. In this situation, thermometer A is in closer proximity to the flame compared to thermometer B. So, thermometer A will experience more direct contact with the hot air around the flame, resulting in a higher transfer of heat through conduction.
2. Convection: This is the transfer of heat through the movement of fluids (in this case, air). As the air around the flame heats up, it expands and becomes lighter, causing it to rise. Thermometer B is placed above the flame, which means it will be in contact with the warm air that rises. Thus, it will experience heat transfer through convection.
3. Radiation: This is the transfer of heat through electromagnetic waves. Both thermometers will receive heat through radiation since they are exposed to the flame. However, the intensity of radiation decreases with distance. Therefore, thermometer A, being closer to the flame, will receive more radiation compared to thermometer B.
Considering these factors, it is likely that thermometer A will show a greater rise in temperature compared to thermometer B. Thermometer A will receive more heat through conduction due to its closer proximity to the flame and also higher intensity of radiation being emitted.
It is important to note that this explanation is based on the assumption that the materials used in both thermometers are the same and have similar thermal conductivity properties.