Deflection Magnetometer-
This is a device which is used to measure the magnetic moment and polar strength of a bar magnet. It consists of a very small magnet, or a magnetic needle piovoted on a sharp support and free to rotate in a horizontal plane. Attached perpendicular to the small magnet in a light, thin and long aluminium pointer.
The pointer also rotates when the magnetic needle roates. The circular scale is graduated into degrees and divided into four quadrants. In order to avoid parallex in reading the ends of the pointer on the circular scale, a plane mirror is laced below the scale and the eye is so polaced that the image of the ointer scale are enclosed in a box with glass top. There are two arms graduated in centimeter scale and the zero of the scale starts from the point where magnetic needle in pivoted.
Comparison of magnetic moments : (tan A - position ) f1 and M2 are the magneitc moments of the two magngts and θA and θB are the deflections of the needle for the same distanc d in each case,then, from tangent law-
Here l1 and l2 are the semi-lenghts of the two magents.
If l1 l2 negligible in comparison to d, then
