PIRA 5C10.20 Capacitance: Parallel Plate Capacitor
Photo Shows the Demonstration Apparatus Used by the University
of Texas at Austin
Set Up Instructions / Notes:
- Demo includes a Wimshurst machine, an adjustable parallel plate capacitor and an open electroscope.
- A red wire is attached connecting the electroscope to the non-moving plate of the capacitor.
- A second red wire is then attached to the first red wire which now connects the fixed plate of the capacitor to an electrode on the Wimshurst.
- This second red wire will be pulled of the fixed plate of the capacitor after charging the demo with the Wimshurst.
- Therefore, the second red wire must fit loosely into the first red wire, if it is to be easily removed from the circuit.
- The double set of black wires are connected to the adjustable plate of the capacitor, electroscope and the second Wimshurst electrode.
Photo Shows the Demonstration Apparatus after charging and subsequent removal of the second red wire from the circuit.
Operating Instructions :
- Adjust the spacing between the plates so that they are separated as far as possible from each other.
- Turn the crank on the Wimshurst machine until the Electroscope needle deflects upwards.
- Quickly remove the red wire lead from the Wimshurst to the parallel plate capacitor, taking care not to disturb the red wire between the electroscope and the capacitor plate.
- Decrease the spacing between the plates and observe the transfer of electric charge from the electroscope to the large parallel plate capacitor.
- Increase the spacing between the parallel plates and observe the needle on the electroscope as it returns to its prevous position.
- A set of dielectric plates are provided with the demonstration to show the effect of inserting a dielectric material.
Last Update 02/08 - University of Texas at Austin Physics Dept.
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