Question Number 33557 by JohnQuinceyStClair last updated on 19/Apr/18
$${This}^{} {is}^{} {a}^{} {formula}. \\ $$$${working}^{} {out}^{} {the}^{} {area}^{} {between}^{} {two} \\ $$$${Toroidal}^{} {coils}. \\ $$$${Both}^{} {with}^{} {a}^{} {magnetic}^{} {spring}^{} {constant}. \\ $$$$ \\ $$$${r}={radius}=\mathrm{1} \\ $$$$\mathrm{a}={area}=\mathrm{2} \\ $$$$ \\ $$$$\mathrm{k}^{\mathrm{z}} =\frac{\mathrm{1}}{\left(\mathrm{r}+\mathrm{a}\right)}−\frac{\mathrm{1}}{\mathrm{r}^{\mathrm{2}} }=−\mathrm{a}\frac{\left(\mathrm{2}\centerdot\mathrm{r}+\mathrm{a}\right)}{\left[\left(\mathrm{r}+\mathrm{a}\right)^{\mathrm{2}} \centerdot\mathrm{r}^{\mathrm{2}} \right]} \\ $$$${ratio}=? \\ $$$${what}^{} {is}^{} {the}^{} {ratio}? \\ $$