'''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 by Henry Augustus Rowland.
The geometry of a Rowland's ring is usually a toroid of magnetic material around which is closely wound a magnetization coil 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 induced magnetic flux. The electric current flowing in the magnetization coil dictates the magnetic field intensity <math>\mathbf{H}</math> in the material. The sampling coil produces a voltage proportional to the rate of change of the magnetic field <math>\mathbf{B}</math> 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. ==See also== *Electromagnetic induction == 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).
Category:Electromagnetism
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