Ans: The transfer of heat on which molecules of a medium move to the source of heat energy to absorb heat and then move away from it is called convection.
Q: How does convection occur?
When water is heated it expands . the expanded water has less weight than the surrounding colder water. the warmer water is pushed upward by the colder water which has more weight. the colder water is heated and then pushed upward . this upward and downward movement of water is called a convection current. the heated water is forced up and later sinks as is cools . when the colder water returns to the bottom , it is heated again.
Convection in liquids:
1: Take a beaker and fill its two-third with water. place the beaker on the stand.
2:Add some saw dist to the water.
3: Now heat the beaker as shown in the figure . note the motion of the saw dust in the water
Convection in Gases:
1:Light a candle and place it under one of the hole in the convection box.
2:Cover the box with plastic sheet.
3:Bring a burning piece of paper/cloth near the hole other than the candle
observe the path of the smoke in the convection box.
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