# Homework Help: Magnetic circuit

1. Dec 17, 2011

### keongie

1. The problem statement, all variables and given/known data
Refer attachment q.

2. Relevant equations
Refer attachment f.

3. The attempt at a solution
Refer attachment t.

Please help, this lecturer likes to give questions that are not taught during exams.

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• ###### t.jpg
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Last edited: Dec 17, 2011
2. Dec 18, 2011

### keongie

Alright, done research online, found the formula of magnetic force of attraction. F = (Bg^2)*Ag/(2*permeability of air). I guess it is the missing piece of the puzzle and the rest of the question should unravel themselves.

Any other opinion or idea? Please do not hesitate to reply.

100% sure that the formula is not found nor taught in class. It is either a killer question to fit the bell curve or whateva it is. My deepest appreciation and gratitude to those who have viewed and tried helping, thanks a million.

3. Dec 19, 2011

### rude man

I would like to check your answers but am unable to read your scanned sheets 2 and 3.

Maybe you could just write down your answers on a separate sheet in LARGE ALPHANUMERICS, then I'll tell you if I got the same answers.

Your formula for force is correct, derived simply from the principle of virtual work (incremental change in energy in the magnetic fields in the three air gaps = force* incremental distance).

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