On the measurement of the effective area of a search coil

A condenser null-method for the determination of the effective area of search coil is described. The underlying principle is to compare the area of the unknow coil with a calculable area, the two coils being used alternately in a powerful, constant magnetic field, of which the region of uniform intensity has been extended by the use of pole-pieces with large area. The flux in each coil as it cuts the field can be exact neutralized by the charge of a condenser. The ratio of the two areas is given as a rat of two resistances. An accuracy to four significant figures is possible.