The region between two concentric spheres of radii ' a ' and ' b ', respectively (see figure), has volume charge density ρ=A/r, where A is a constant…

The region between two concentric spheres of radii ' $\displaystyle a$ ' and ' $\displaystyle b$ ', respectively (see figure), has volume charge density $\displaystyle \rho=\frac{A}{r}$, where $\displaystyle A$ is a constant and $\displaystyle r$ is the distance from the centre. At the centre of the spheres is a point charge $\displaystyle Q$. The value of $\displaystyle A$ such that the electric field in the region between the spheres will be constant, is :