Electricity and Magnetism > Magnetic Materials DCS# 5G40.10

HYSTERESIS CURVE

hysteresis curve setup

APPARATUS
toroid with ferrite core
214-01-G2
6.3 V transformer
107-01-C
integrator/amplifier circuit
214-03-G1
DC power supply
214-01-C
30 ohm and 5.6 ohm variable resistors
202-19-F
oscilloscope with camera
202


DESCRIPTION
The B vs H curve of the ferromagnetic core is displayed on an oscilloscope:

hysteresis curve.

NOTES

The scope should be in x-y mode.  Display the current in the primary coil (voltage across the resistor), which is proportional to the applied field H, on channel 1.   The integrated output of the secondary coil, which is proportional to the magnetic induction B, is displayed on channel 2.

If using a resistor other than the 5.6 ohm rheostat, use AC coupling on channel 1 or the curve will be distorted.
hysteresis circuit
toroid and fry daddy
Curie temperature:

It can be shown that the magnetization goes to zero at the Curie temperature by heating the coil to ~ 150°C.

Heat the coil in 3 cups of canola oil in a Fry Daddy (214-03-F).  It takes about five minutes to reach the Curie temperature.

REFERENCES
Chin-Shan Lue, A Direct Method for Viewing Ferromagnetic Phase Transition, TPT 32, 304-305 (1994).