5A20.37 - Coulomb's Law Balance - Pasco Model

Code Number:
5A20.37
Demo Title:
Coulomb's Law Balance - Pasco Model
Condition:
Good
Principle:
Electrostatics, Coulomb's Law
Area of Study:
Electricity & Magnetism
Equipment:
6 KV power supply, Coulomb's Law balance (Pasco Model), charging paddles, high voltage charging probe.
Procedure:

Zero the torsion pendulum before putting charge on the balls.  Set the power supply at 5000 volts and touch one or both of the balls.  Electrostatic repulsion or attraction can be shown and measured with this device.

An interesting variation is to use only the torsion balance part of the apparatus and a metal plate.  When the ball is charged, a "mirror charge" will be induced on the plate.  The ball on the torsion balance will swing over, touch the plate, then be repelled.

A discrepant event of the above demo is to use the black painted plate instead of the bare metal plate.  In this case the ball will stick to the metal plate.

References:
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  • W. Bolton, "Potential", Book 4 - Electricity, Physics Experiments and Projects, 1968, p. 24 - 25.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.