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if a bar magnet of magnetic moment M be bent to a semicircular magnet of radius R, then what will be its magnetic moment?

Hello soumitra,

The general formula for magnetic moment of a semicircular magnet (interpreting semicircular as any fraction of a circle) is
M1 = [2*M*sin(theta/2)] / theta
where theta is in radians. If the semicircle is 180 degrees of arc, or pi radians of arc, that formula reduces to
M1 = 2*M/pi

8.c in section titled MAGNETIC MOMENT
3. in section titled Unsolved Problem

I hope this helps,


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Steve Johnson


I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.


I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University

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