Problem 3.21

A ball of radius \(R\) is uniformly charged with the volume density \(\rho\). Find the flux of the electric field strength vector across the ball's section formed by the plane located at a distance \(r_{0} < R\) from the centre of the ball.

|\Phi|=1 / 3 \pi \rho r_{0}\left(R^{2}-r_{0}^{2}\right) / \varepsilon_{0}

Constant Electric Field in a Vacuum