Page:Scientific Memoirs, Vol. 1 (1837).djvu/639

Rh in terms of the diameter of the cylindrical armature, and the thickness of the wire and its silky envelope. We have however the semi-diameter of a convolution, if half the thickness of the iron cylinders is $${}= q$$, whence we have the length of a convolution or If we substitute the first value of $$c$$ in the equation for $$m$$, we obtain

The electromotive power is for two series of convolutions with regard to the above law, No. 2, but the resistance is equal to that of the two series of convolutions, together with the piece $$m$$, therefore consequently the power of the current for two series, or