Question

Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?

Answer 1

Step 1: Structure of candle flame

• Outermost nonluminous zone of complete combustion: This zone is faintly visible and surrounds the yellow luminous part of the flame. In this zone, the wax vapour undergoes complete combustion because plenty of air is present around it. This zone is the hottest part of the candle flame.
• Central (or middle) luminous zone of incomplete combustion: The central luminous zone is the major part of the candle flame. This zone is bright yellow and luminous and lies below the outermost nonluminous zone. In this zone, wax vapor undergoes incomplete combustion because not enough air is present here. The incomplete combustion of wax vapor produces carbon particles. These unburnt carbon particles get heated up and start glowing. These glowing carbon particles make the flame luminous. Thus, the central zone of the candle flame is luminous due to the incomplete combustion of wax vapor in this zone.
  This part of the flame has a moderate temperature.
• Inner dark zone of no combustion: The dark zone around the wick is called the inner dark zone of no combustion. In this zone very little or no combustion takes place because in this zone no air is present. This part of the flame is the least hot.

Step 2: Conclusion

• Abida kept the beaker near the wick in the yellow part of the candle flame. This part of the flame has a moderate temperature.
• Ramesh kept the beaker in the outermost part of the flame. This zone is the hottest part of the candle flame.
• Ramesh's water will get heated in a shorter time.

Hence, Ramesh's water will get heated in a shorter time.