Question

An electron of mass $Mkg$ and charge $ecoulomb$ travels from rest through a potential difference of $Vvolt$. The final velocity of the electron is $\left(inm/s\right)$ :

• A. $\frac{2eV}{M}$
• B. $\frac{2MV}{e}$
• C. $\sqrt{\frac{2eV}{M}}$
• D. $\sqrt{\frac{2MV}{e}}$

Answer 1

The correct option is C $\sqrt{\frac{2eV}{M}}$

Energy gained by an electron $=q\Delta V$
$=V\times e$
this energy is in the from kinetic energy
$\Rightarrow \frac{1}{2}M{v}_f^2=V\times e$

$\Rightarrow v_f^2=\frac{2eV}{M}$

$\Rightarrow v_f=\sqrt{\frac{2eV}{M}}$