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Re: osmosis question

Posted by alexandra_k on September 3, 2014, at 18:14:09

In reply to Re: osmosis question, posted by alexandra_k on September 3, 2014, at 17:04:18

i think height is important...

something something i'm supposed to know (but i don't feel like i understand it properly) about measuring atmospheric pressure with reference to the height a column of mercury will reach.

so you have this dish of mercury open to the air... and if you stick a small tube with a closed end (e.g., a narrow test tube) into the dish then the mercury will start to climb up the tube... the idea being that the atmospheric pressure of the air molecules bouncing on the mercury in the open dish... is greater than the gravity pressure down on the mercury in the tube... and the mercury climbs up the tube...

to a height of 270 millimeters. at sea level. so 270mm (millimeters) Hg (mercury) is atmospheric pressure at sea level.

i has been learning :)

but that should surely depend on the width of the column of mercury... i would have thought... like how capillary action for water depends on the width of the capillaries. i think. and perhaps also on the surface area of the mercury that is being bombarded by air molecules...

anyway... height is important because of potential energy... you can put a tap in the higher bit and water will flow out the tap to the lower bit. you could use the flow of water to power a motor or something...

but i guess energy went into putting the rock in there in the first place...

i really... shouldn't think about such stuff. it feels to be... nonsense. on some level. i don't know what to say.

my textbooks is quite clear that a bunch of metal (hollow or solid, of any shape) will form a farraday cage *unless a current is running through it*. dammit. i missed that last bit. got myself all into a state about how current must be conducted along the surface of a wire and not through the middle of it :(

 

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