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Uploaded on Aug 8, 2008
Two large coils of wire ("Helmoholz coils") are connected to 125V DC power, and produce a uniform magnetic field between the coils.Â A separate coil is suspended with this field.Â Switching the polarity of the DC current in the inner coil causes it to rotate in opposite directions.
This principle is used by devices called galvanometers to measure electric current.