Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538
Demonstrations are cataloged according to PIRA Bibliography
PLEASE REQUEST DEMOS WELL IN ADVANCE
Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.
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You have selected the following Demos:
Purpose:To show the competing effect of surface tension of a fluid and the adhesive forces between a liquid and a glass surface.
Procedure:A set of seven glass capillary tubes are set up to draw liquid from a common resevoir. Adhesive forces cause the liquid to rise up the sides of the tubes while the surface tension of the liquid causes a column of water to be pulled up the tube. Given the same adhesion forces and surface tension in each tube, the height of the liquid in each tube will depend on the weight of the liquid lifted so that the water level will be higher in tubes with a smaller diameter.
Hints:If the tubes are not wetting properly, heat them in a bunsen burner flame very slowly and evenly so as not to crack the glass. Once you see a bit of yellow flame around the tube, that is enough. Let them air cool on a glass dish or some other insulating material so they don't cool too quickly and crack.