Question 2.39: Find C if Q = 1/R√L/C where Q = 10, R = 40Ω, L = 1.0

Q R=\sqrt{\frac{L}{C}}

and squaring both sides gives:

(Q R)^2=\frac{L}{C} \quad \text { or } \quad Q^2 R^2=\frac{L}{C} \\ C\left(Q^2 R^2\right)=L \quad \text { then, } \quad C=\frac{L}{Q^2 R^2}.

Substituting for the given values, we get:

C=\frac{1.0}{10^2 40^2}=6.25 \times 10^{-6} Farads.