The Ampere circuital law, that the line integral of the magnetic field around a closed path depends only on the total enclosed current and not on the shape of either the current or the integration path, may be strikingly demonstrated. The setup for this is based on the electromagnetic induction taking place in a fine helical coil wound on a nearly closed iron loop. The construction and theory of this device is discussed. Its operation is similar to that of a standard ac ‘‘clamp‐on’’ ammeter. The method is simple and can be carried out very quickly. Some analog demonstrations of magnetic flux are also described. These experiments are related to the circuital law demonstration through the electromagnetic reciprocity theorem.
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© 1992 American Association of Physics Teachers.
1992
American Association of Physics Teachers
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