Question

An electron is moving around the nucleus of a hydrogen atom in a circular orbit of radius r. The coulomb force $\vec F$ between the two is- (where K=$\frac{1}{4\pi\epsilon_0}$)

• A. $K\frac{e^2}{r^2}\hat r$
• B. $-K \frac{e^2}{r^3}\hat r$
• C. $K\frac{e^2}{r^3}\vec r$
• D. $-K \frac{e^2}{r^3}\vec r$

Answer 1

Answer: (D)

$-K \frac{e^2}{r^3}\vec r$

Answer 2

Coulomb force = $K \frac{e^2}{r^2}(-\hat r)$
=$K\frac{e^2}{r^3}\vec r$