Why does smoke always rise upwards?

  • Thread starter rohanprabhu
  • Start date
  • Tags
    Rise Smoke
In summary, the reason for smoke rising is due to convection currents caused by hot air rising and displacing cold air. The "fluid" surrounding the burning object is cold air and without it, smoke would not rise. Hot air will seek out the nearest opening, which may not always be vertically upward. Burning in a vacuum is not possible without a source of oxygen.
  • #1
rohanprabhu
414
2
First i thought that smoke used to rise upwards due to a 'projection' created by a chimney.. but lately when I was looking at an essence stick.. the smoke could literally go anywhere. Even the same with a burning piece of coal. Even the smoke generated at the bottom part of the coal 'envelopes' around the piece of coal and rises upwards.

No matter what orientation we select, the smoke always rises upwards. By 'upwards' I mean 'opposite and along the line of force of gravity'.

So.. what exactly is the reason of this happening? My best guess is that this is due to another fluid surrounding the burning object as well as acting as a medium for the travel of smoke [i.e. air]. So.. if i burn a piece of coal in vacuum [just believe that for know we have some oxygen bubbles in the coal itself or something].. will the smoke move around in all directions despite the effect of gravity?
 
Physics news on Phys.org
  • #2
Smoke rises for the same reason 'hot air' rises, convection currents.

Nice Avatar by the way :wink:
 
  • #3
"Smoke", strictly speaking, consists of particles of ash carried on the hot are from burning. Since hot air is less dense than cold air, it rises as it is displaced by the heavier cold air. I suppose you could say that the "fluid" you are talking about is the cold air. Actually, with the particles of ash, the density is not a great deal less than that of cold air- smoke does not always rise. Depending on the circumstances, it can stay close to the ground.

You cannot have ordinary burning in vacuum- no oxygen. If you were to use a substance that contained its own oxygen, say sodium peroxide, the vapors that came off in vacuum would not rise.
 
  • #4
rohanprabhu said:
My best guess is that this is due to another fluid surrounding the burning object as well as acting as a medium for the travel of smoke [i.e. air]. So.. if i burn a piece of coal in vacuum [just believe that for know we have some oxygen bubbles in the coal itself or something].. will the smoke move around in all directions despite the effect of gravity?

Hi rohanprabhu! :smile:

I think you're right - the smoke heats the air, and then the hot air rises, causing a draught, which carries the smoke with it. :smile:

The draught will seek out the nearest suitable opening, whch is not necessarily vertically upward … so if you have no chimney, but just make a small hole in the roof, the smoke from a fire should head straight for the hole, instead of filling the room.

I don't think your vacuum suggstion would be very helpful, though - wouldn't anything automatically fill the vacuum?
 
Last edited:
  • #5
thanks to everybody.. that cleared it up for me.. thanks a lot to HallsOfIvy...

Hootenanny said:
Nice Avatar by the way :wink:

totally.. :D
 

FAQ: Why does smoke always rise upwards?

1. Why does smoke rise upwards?

Smoke rises upwards because of the principle of buoyancy. Hot air is less dense than cold air, so it rises. When smoke is released, it mixes with the surrounding air and becomes hot, causing it to rise upwards.

2. Does smoke always rise upwards?

No, smoke does not always rise upwards. In certain conditions, such as when there is a strong wind, smoke can be blown in different directions. However, in most cases, smoke will rise upwards due to the principle of buoyancy.

3. Can smoke rise downwards?

No, smoke cannot rise downwards. The principle of buoyancy dictates that hot air, and therefore smoke, will always rise upwards. However, smoke can be pushed downwards by external forces such as wind or air conditioning systems.

4. Why does smoke rise in a straight line?

Smoke typically rises in a straight line because it is affected by the surrounding air currents. These air currents can be caused by wind or temperature differences, which can cause the smoke to move in a particular direction as it rises.

5. How does smoke rising affect air quality?

Smoke rising can have a negative impact on air quality if it contains pollutants or toxins. These substances can be harmful to human health and the environment. However, the direction in which the smoke rises can also affect air quality, as it can disperse pollutants over a wider area and reduce their concentration in a specific area.

Back
Top