NMT-Physics Intranet

Interaction between neutral and charged objects.

Demonstrates that charges of opposite signs attract each other. Start by rubbing a piece of acrylic with rabbit fur and then bring the acrylic close to a bunch of small pieces of paper. Notice how the paper flies over toward the acrylic. Now put a aluminum soda can over a flat surface, so it is able to roll, then bring the chargedacrylic piece close to the can and slowly move it away from the can. Observe how the can follows the acrylic. In order to make sense of the observations, one has to remind the audience that neutral objects are not void of charge, but are in a state of charge balance. Also thattheir charge can be reorganized in response to an external electric charge. For instance, polarization of molecules in non-conducting materials (like the pieces of paper and Styrofoam) and mobility of electrons in the case of conductors (like the soda can). This demonstration is perhaps more effective if you show the students that regardless of the type of charge the neutral object is attracted to the charged object. See the "Electric Charge" demo to show that two charged objects have opposite charge.

ID: d0009

Set up time:

2 minutes in class.

Requires:

Notes:

You may need assistance the first time you use this demo.Check the forecast. If is going to be humid the demo may be hard to convey. When rubbing rabbit fur on acrylic, the rabbit fur is happy to donate electrons and become positive charged. You may also use silk and Teflon.

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