FLAME DIRECTION
When we light a lamp, it always burns in the upward direction, why?
INDU. C THRISSUR, KERALA
A flame is a burning gas drawing fuel through a wick or from a fuel pipe (as in case of gas stove). The burning gas is at a very high temperature, making it much lighter in density as compared to the surrounding air at room temperature. As we know a lighter substance always moves against the gravity when dipped in a medium of heavier density, so is the case in a flame. As the hot gas is pulled in the upward direction, the vacuum caused is filled up by surrounding gases comprising oxygen, nitrogen etc. The oxygen accelerates the burning of fuel and the flame is sustained till the fuel exhausts. Another interesting observation about the flame is that the shape of the flame is narrow at the top as it goes up and up. This is because as the gases are pushed up, their velocity increases. As the velocity increases, the diameter reduces as at every section vertically, same amount of gases are passing. In a media with no gravity, such as in the space, it is difficult to predict which way the flame would turn and it all depends on the difference in density of gases around the flame. With no gases around, the flame would normally be spherical in shape.
S.P.S. JAIN
Greater Noida
THIS WEEK’S QUESTION
Why does it rain heavily all of a sudden, while at times it takes a while for it to become heavy?
Vasudev, Chennai
