- Rowland ring
Rowland's ring (aka Rowland ring) is an experimental arrangement for the measurement of the
hysteresis curve of a sample of magnetic material. It was developed byHenry Augustus Rowland .The geometry of a Rowland's ring is usually a
toroid of magnetic material around which is closely wound a magnetizationcoil consisting of a large number of windings to magnetize the material, and a sampling coil consisting of a smaller number of windings to sample the inducedmagnetic flux . Theelectric current flowing in the magnetization coil dictates the magnetic field intensity mathbf{H} in the material. The sampling coil produces a voltage proportional to the rate of change of themagnetic field mathbf{B} in the material. By measuring the time integral of the voltage in the sampling coil versus the current in the magnetization coil, one obtains the hysteresis curve.External links
[http://physics.kenyon.edu/EarlyApparatus/Electricity/Rowlands_Ring/Rowlands_Ring.html Photo of a Rowland's ring]
References
Paul Lorrain and Dale Corson, "Electromagnetic Fields and Waves, 2nd ed", W.H. Freeman and Company (1970).
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