## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

$E = 1200~N/C$
Let $V$ be the volume of the space. We can find the strength of the electric field $E$: $\frac{U}{V} = \frac{1}{2}\epsilon_0~E^2$ $E^2 = \frac{2U}{V\epsilon_0}$ $E = \sqrt{\frac{2U}{V\epsilon_0}}$ $E = \sqrt{\frac{(2)(50\times 10^{-12}~J)}{(0.020~m)^3(8.854\times 10^{-12}~F/m)}}$ $E = 1200~N/C$