Demos: 5A-33 Current Along a Poor Conductor


One end of a long wooden dowel rod is connected to an electrostatic generator. The other end is grounded. Three different points along the rod are connected to identical electroscopes (Braun). The electroscope nearest the generator shows the greatest deflection, the second nearest the second greatest deflection and so on. This shows that electric charge flows along the rod and that a potential difference exists along the rod. When the ground connection is removed, all three electroscopes have the same reading.

Directions: Lay the dowel rod across the plates of the electroscopes, relatively evenly spaced. Be sure to discharge all three electroscopes before charging. Ground one end of the rod and connect the other to the ESG.

Suggestions for Presentation: Ask first if there should be any reaction at all from the electroscopes since wood is supposedly a non-conductor. If students say that the voltage is so high that some breakdown occurs, ask if there should be a reaction from the electroscopes or will the charge go directly to ground? If not, will all electroscopes read the same?

Applications:

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Last Updated: May 9, 2016 11:44 AM