Question

Consider an atom with atomic number $Z$ as consisting of a positive point charge at the centre and surrounded by a distribution of negative electricity uniformly distributed within a sphere of radius $R$. The electric field at a point inside the atom at a distance $r$ from the centre is

• A. $\frac{Z e}{4 \pi \varepsilon_{0}}\left[\frac{1}{r^{2}}-\frac{r}{R^{3}}\right]$
• B. $\frac{Z e}{4 \pi \varepsilon_{0}}\left[\frac{1}{r^{2}}+\frac{1}{R^{3}}\right]$
• C. $\frac{2 Z e}{4 \pi \varepsilon_{0} r^{2}}$
• D. Zero

Answer 1

Answer: (A)

$E=E_{1}-E_{2}$
$E=\frac{k . z e}{r^{2}}-\frac{k \,z e r}{R^{3}}$