The magnetic circuit of figure consists of a core and a moveable plunger of width l_p, each of permeability ?. The core has cross-sectional area A and means length A_c. The overlap area of the two air gaps Ag is a function of the plunger position x and can be assumed to vary as you may neglect any fringing fields at the air gap and use approximations consistent with magnetic-circuit analysis.

a. Assuming that ? ? ?, derive an expression for the magnetic flux density in the air gap B_g as a function of the winding current I and as the plunger position is varied (0 x 0.8 X₀). What is the corresponding flux density in the core?

b. Repeat part (a) for a finite permeability ?.

Transcribed Image Text:

Ag = Ac (1- Xo Core: mean length l area A X, N turns Plunger