Question

we blow on the burning pieces of wood while cooking in a chullah

Answer 1

When we blow the air on glowing wood it catches fire.But at the same time, we use a blow of air to extinguish the flame of a candle .why

In olden times when we used to cook the food on chulha , we used to light the papers , dry grass or some pieces of wood. It would not catch the fire so we used to blow the air from a pipe so that it could catch fire instantly. But at the same time, we use a blow of air to extinguish the flame of a candle .

Another Answer:

Oxygen is necessary for combustion. Blowing out a candle makes the candle goes out. Because in candle the flame is due to burning of vapoutized wax. When we blow the candle the vapourized wax is removed from the heat source and the candle flame goes out. Where as in the case of wood blowing on glowing wood or charcoal will make it burn faster. When you blow the fuel cannot move away. Here while blowing your adding air to the fuel so it catches fire easily.

Answer 2

Answer:

By blowing on burning wood or coal we are maintaing a continuous supply of oxygen which is required by the fuel( wood / coal ) to keeping burning.

Explanation:

Blowing also removes the CO2 layer formed which is released by the burning fuel and acts as an extinguisher .