The force carried by the plunger of the door chime in Fig. 1 is determined by where dϕ/dx...

The force carried by the plunger of the door chime in Fig. 1 is determined by

where dϕ/dx is the rate of change of flux linking the coil as the core is drawn into the coil. The greatest rate of change of flux occurs when the core is ¼ to ¾ the way through. In this region, if Φ changes from 0.5 × 10−4 Wb to 8 × 10−4 Wb, what is the force carried by the plunger?

FIG. 1

Door chime