Hysteresis: Magnetism Lags Behind Current

[uzair_ha91]

Can anyone explain the following lines? [Only the bit where the letters are capitalized]
"The flux density versus the magnetization of the specimen for the various values of the magnetizing current of the solenoid is plotted by a CRO...from the figure, we can conclude that value for flux density for any value of current is always greater when current is decreasing than when it's increasing, I.E. MAGNETISM LAGS BEHIND THE MAGNETIZING CURRENT. This phenomenon is known as hysteresis."

 

[turbo]

Hysteresis exists in systems in which effects lag causative mechanisms, so there is not a reliable way to predict the instantaneous state of the system without having an understanding of the history of the system. When the magnetizing current is increasing, the magnetic flux is also increasing, but lagging the increase in current. When the magnetizing current is decreasing, the magnetic flux also reduces, but is stronger than one might expect (calculating from instantaneous values) because of the time it takes for the flux to moderate as the magnetizing current is removed. The capitalized portion of your post explains that the magnitude of the magnetic flux in the system rises and falls with the magnitude of the magnetizing current BUT these changes in flux take time to occur and always lag behind the changes in current.

 

[Bob S]

Here in thumbnail is a page extracted from Wikipedia on hysteresis. The horizontal axis is the current in amps (amp turns per meter) and the vertical axis is field strength (Tesla). When a hysteresis curve data is neasured, the measurement points go around the loop in a counterclockwise direction. For a given number of amps, the field is higher (lagging) when the direction of the current is decreasing.

 

[uzair_ha91]

Thanks for the efforts, the answers you guys posted have cleared my misconceptions about hysteresis :-)

 

[uzair_ha91]

And I think there's a typo in my post [the 1st line of the text I quoted] : "The flux density versus the magnetization CURRENT of the ..."