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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video - Gauss' LawPurpose:To show that excess charge resides totally on the outside of an insulated conductor.Procedure: Charge the metal cylinder by touching it inside with a Teflon rod (charged with fur or silk) a few times. Show that there is a charge on the cylinder by bringing it close to the electroscope. Then lower the ball into the top opening of the cylinder making sure not to touch the edges. Extract the ball with the same care after banging it around inside the cylinder. Bring the ball near the electroscope and note the absence of charge. Now touch the outside of the cylinder with the ball and demonstrate with the electroscope that the ball is charged. Hints:Be patient and careful. Ground the cage before the first trial, ground the ball on the rod between the sets, be mindful of not touching the edges of the cylinder while extracting the stick from inside.On the Pasco ES-9054B Electrometer, it is best to use a scale setting of 30 or 100 Volts. Here is the instruction manual. In case of wet weather, one can use the following trick: charge the cup with a Wimshurst machine (lots of charge that doesn't leak off very fast) and instead of electroscope use a pith ball. When attempting to take charge from the inside surface of the cup, the ball will stay immobile, while when attempting to take charge from outside surface of the cup, the ball will deviate. Equipment:
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