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Old Oct 6th 2011, 09:36 PM
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Default Science Question

When one has an oil lamp and lights the wick, it will burn for many hours - until the oil runs out.

My question is, how does this actually work? What force or process draws the liquid oil continuously up the wick?
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Old Oct 6th 2011, 09:49 PM
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Default Re: Science Question

Capillary action.

From wikipedia:
"Capillary action, or capillarity, is the ability of a liquid to flow against gravity where liquid spontaneously rises in a narrow space such as a thin tube, or in porous materials such as paper or in some non-porous materials such as liquified carbon fibre. This effect can cause liquids to flow against the force of gravity or the magnetic field induction. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces; If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and forces of adhesion between the liquid and container act to lift the liquid."
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Old Oct 6th 2011, 10:18 PM
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Default Re: Science Question

Incidentally, I find this process intriguing from an energy standpoint.

One might imagine a system consisting of a wick or cloth partially submerged in liquid. The gravitational potential energy (U=mgh) of the system will steadily increase as the liquid travels up the cloth/wick without any energy being added to the system. And the movement of the liquid against gravity itself would seem to represent kinetic energy that wasn't previously present.

There must be some sort of 'absorption potential energy' (i.e. energy related to the dry cloth/wick's ability to absorb liquid) that is 'expended' as it gets wet. But I don't know what to call that.
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Old Oct 7th 2011, 06:55 PM
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Default Re: Science Question

Quote:
Originally Posted by dilettante View Post
Capillary action.

From wikipedia:
"Capillary action, or capillarity, is the ability of a liquid to flow against gravity where liquid spontaneously rises in a narrow space such as a thin tube, or in porous materials such as paper or in some non-porous materials such as liquified carbon fibre. This effect can cause liquids to flow against the force of gravity or the magnetic field induction. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces; If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and forces of adhesion between the liquid and container act to lift the liquid."
Thanks for that!

Actually, as soon as I saw the name "capllary action" I remember this from high school science classes. I guess I just forgot all about it.
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