1. The problem statement, all variables and given/known data The problem can be found http://whites.sdsmt.edu/classes/ee382/homework/382Homework1.pdf" [Broken] (the last one), along with a picture of the circuit. 2. Relevant equations R = l/(µS) mmf = NI = ΨR B = Ψ/S 3. The attempt at a solution I've never done a problem like this before. I've looked for information and example problems to help me do it in my book and online, but I haven't found anything that can help me. The part about it that really confuses me is the use of the plunger. Does it move? If it does, how do I know what the length of the gap is? If it doesn't, do I just ignore the part of the plunger that is below the rest of the circuit because it acts like an open circuit (I don't know if that's true or not)? I was hoping someone here could help me figure out what to do. Thanks.