# sir, how to find the mag. field at the centre of equilateral...and explain it even in case of rectangle of length l and breadth b....

23 Points
14 years ago

Dear Vineet,

We should solve this problem by vector method.

Suppose three poles are placed at three corners of an equilateral triangle then at the centre of the triangle the field would be the resultant sum of the three field vectors. In the triangle case the resultant of two forces are calculated and again the resultant of the third vectror and the resultant of the first two are calculated.

As the distances of the vertices fron the centre of the triangle are same , if all the poles are of equal strength and are like poles  then we get resultant field as zero.

In the square case two reultant fields are calculated seperately  for two pairs of field vectors and then the resultant field of the two obtained resultant fields is calculated as shown in the figure. In this case also if the poles are like then net field inside is zero otherwise they are calculated.

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