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- Homework Statement
- The problem statement is as follows:

- Relevant Equations
- Energy stored in a magnetic circuit=

E=(1/2)*Flux linkage*Current

Force on a movable part in the magnetic circuit=

F= -dE/dx.

Here, I have assumed very quick movement of the moving part. So, as per the mmf-flux curve, flux linking with the system will be unchanged during the movement. To support this assumption, I have made use of the following analysis.

In this graph, the movement of the part happens quickly (small air gap), hence, the the flux linkage will remain unchanged (line PQ) throughout this small interval.

I hope I have sufficiently presented my attempt at a solution. Sorry for the messy white-board though.

The answer I got is F=282.4N but the answer according to the official answer key is 188N.

Where did I go wrong here? Any help is appreciated.