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Lecture Demonstrations Laboratory


The Demonstrations Manual


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Electrostatics
Kinds of Charge and Charging
Attraction and Repulsion Between Charged Objects
Charging by Induction
Lord Kelvin's water-drop electrostatic generator
Xerox
Electric Fields And Potential
Capacitance
Current and Resistance
Electromotive Force And Current
DC Circuits
Magnetic Materials
Magnetism
Inductance
Induction
Complex Circuits
Semiconductors And Tubes
Transmission Lines and Antennas

Charging by Induction

Purpose:

To demonstrate charging of objects by induction.

Procedure:

Use the Faraday's cage as a reliable electroscope that also measures the charge sign. Rub Teflon stick on silk (should produce a negative charge) or Glass/lucite on Teflon wrap (to produce a positive charge) and transfer it to a pith ball on a stick by touching. Measure the charge with electroscope. Next reset the electroscope and charge the pith ball by induction. Do so by short circuiting the pith ball to the metal handle with your palm and finger. Bring the charged object close and "disconnect" the ground by removing the finger from the ball. Demonstrate on the electroscope that the charge on the ball is now opposite to what it was while charged by touching.

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