Note on the Alternating Current Resistance of Single Layer Coils

In a previous paper a formula was derived which involved a function $u_n$ whose values were given only for coils with a ength $b$ not greater than the diameter $2a$. Values are now given for longer coils with values of $\frac{b}{2a}$ from 1 to $\infty$. The original formula is also modified to include closely wound coils by the introduction of new coefficients whose values are given for various ratios of the wire diameter $d$ to the wire spacing $D$. Comparison of computed values with measurements made by Hickman for coils with $\frac{b}{2a}$ between 3 and 12, shows for the original formula a maximum discrepancy of +30 per cent (instead of 300 per cent as given by Hickman) and for the modified formula an average difference of only +7 per cent (calc.-obs.).