5H40.40 - Current Balance

Code Number:
Demo Title:
Current Balance
Magnetic Fields Around Current Carrying Wires
Area of Study:
Electricity & Magnetism
Variac, 6 Volt - 15 Amp Transformer, Amp Meter, Current Balance Apparatus, Laser.

Arrange the apparatus as shown. Adjust the balance so that it moves freely and the top wire is just balanced above but not resting on the bottom wire. Adjust the pitch of the mirror so that the laser reflection will show clearly on the classroom screen. Turn up the Variac but watch the amp meter and do not exceed 15 amps. The parallel wires will repel each other farther as more current is applied. The laser reflection may be observed and/or measured.

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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.