3 The force carried by the plunger of the door chime is determined by do NI dx (newtons) where do/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 4 to '/ the way through. In this region, if changes from 0.5 x 10-4 Wb to 8 x 10-4 Wb, what is the force carried by the plunger? 4 cm- Chime Plunger = 900 mA N = 80 turns Sol: f = 1.35 N Problem 4 Determine the current /1 required to establish a flux of = 2 x 10- Wb in the magnetic circuit Sheet steel 0.002 m N = 200 turns, 0.3 m Sol: I = 32 A 2=0.3A N = 40 turns Area (throughout) = 1.3 x 10 m