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 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 $mathbf\{H\}$ in the material. The sampling coil produces a voltage proportional to the rate of change of the magnetic 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).