Question

An electron of mass $m$ and charge $e$ is accelerated from rest through a potential difference V in vacuum. The final speed of the electron will be

• A. $V\sqrt{e/m}$
• B. $\sqrt{eV/m}$
• C. $\sqrt{2eV/m}$
• D. $2eV/m$

Answer 1

Answer: (C)

$\sqrt{2eV/m}$

Answer 2

Kinetic energy $K = \frac{1}{2}mv^{2} = eV$

⇒ $v = \sqrt{\frac{2eV}{m}}$