Coulomb's Law in Vector Form

2003 AIPMT 1 question

1. 1 Electric Charges and Fields Medium
   An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius r. The coulomb force $\vec{F}$ between the two is - (where $K = \dfrac{1}{4\pi\varepsilon_0}$)
   A $K\dfrac{e^2}{r^2}\hat{r}$ B $-K\dfrac{e^2}{r^3}\hat{r}$ C $K\dfrac{e^2}{r^3}\vec{r}$ D $-K\dfrac{e^2}{r^3}\vec{r}$
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