Magnetometry

The determination of the magnetic moment of a magnet. It involves the determination by experiment of--( a) the product of the magnetic moment, M, of the magnet by the horizontal component, H, of the earth's magnetism; (b) the quotient of M divided by H. Knowing these two quantities, M is given by the formula M = Square Root( )M * H) * (M/H) ) and if desired H is given by the formula H = Square Root( (M*H) / (M/H)). M*H is determined by the method of vibrations. A very long, thin magnet suspended by a torsion filament is caused to oscillate, and its period is determined. Calling such period T and the moment of inertia of the magnet I, we have the formula T= 2* PI * Square Root( I / (H*M) ) (a), whence H*M is calculated, I of course being known or separately determined. IMG:8956969607833025625_364F233.jpg: Fig. 233 END-ON METHOD. IMG:8956969607833025625_364F234.jpg: Fig. 234. BROADSIDE METHOD. M/H is determined by the End-on deflection method, or the Broadside deflection method. In both cases the deflection of a compa needle by the magnet in question is the basis of the work. In the end-on method AB is the magnet under examination; DE the compa needle; a the angle of deflection; d  the distance between C and the middle of AB, which should be considerable compared with the length of DE; 2l, the length of AB. We then have the formula tan a = (M/H) * (2d / (d^2 - l^2)^2), which if 2l is small compared to d reduces to tan a = M/Hd 3 (b), which gives M/H, a and d being known. 365   STANDARD ELECTRICAL DICTIONARY. In the broadside method the line d is the magnetic meridian, and the diagram shows the relative positions. We then have the formula tan a = (M/H) / (d2 + l2)^1.5; which if 1 is relatively small reduces to tan a = M/(H * d3 )(C.) IMG:8956969607833025625_365PIC.jpg: [Transcriber's note: The image of the above paragraphs is included here.] a and c or a and b can be combined giving M and H in C.G.S. measurement.