Demagnetizing Sentence Examples
Demagnetizing Force.-It has already been mentioned that when a ferromagnetic body is placed in a magnetic field, the resultant magnetic force H, at a point within the body, is compounded of the force H o, due to the external field, and of another force, Hi, arising from the induced magnetization of the body.
Since H, generally tends to oppose the external force, thus making H less than H o, it may be called the demagnetizing force.
Except in the few special cases when a uniform external field produces uniform magnetization, the value of the demagnetizing force cannot be calculated, and an exact determination of the actual magnetic force within the body is therefore impossible.
Since I =KH, we have KH I-KNI =KHo, (30) or H =Ho-NI, NI being the demagnetizing force H i.
The demagnetizing force inside a cylindrical rod placed longitudinally in a uniform field Ho is not uniform, being greatest at the ends and least in the middle part.Advertisement
Denoting its mean value by Hti, and that of the demagnetizing factor by N, we have H=Ho-Hti=Ho-NI.
With these arrangements there is no demagnetizing force to be considered, for the ring has not any ends to produce one, and the force due to the ends of a rod 400 or 500 diameters in length is quite insensible at the middle portion; H therefore is equal to Ho.
In all such measurements a correction should be made in respect of the demagnetizing force due to the joint, and unless the fit is very accurate the demagnetizing action will be variable.
Since the demagnetizing factor was o 052, the strongest field due to the coil was about 1340; but though arrangements were pro vided for cooling the apparatus by means of o ice, great difficulty was experienced owing to heating.