1.

The core and the armature of an electromagnet with dimensions in millimeters as shown in Fig. 30.16 have been manufactured from a ferromagnetic material whose properties have been described in Problem 29.10. What is the force with which the core attracts the armature, if the material has been magnetized to saturation? What force will remain active after the current is switched off?

Answer»


Solution :In the case of a good CONTACT of the armature with the core, the force of altraction of one pole is `F w_m S.` Therefore the armature as a whole is attracted with the force `F=2w_(m)S B^2S//mumu_(0)` where `S=60 xx 60 xx 10^(-6)m^2=36 xx 10^(-4) m^2` is the core cross section (see Fig. 30.16). SINCE we assumed the gap between the armature and the core to be negligible, we may assume the induction of the field to be the same in the gap as in the core. The magnetic permeability in the gap, on the other hand, is unity `MU= 1).`
We have `F_("sat")=B_(x)^2 "at" S//mu_(0)` in case of saturation magnetization and `F_(r)=-B_(r)^2 S//mu_(0)` in the case of residual magnetization. The values of `B_("sat") and B_(r)` are presented in the table following Problem 29.10 (see alsu fig. 29.10)


Discussion

No Comment Found

Related InterviewSolutions