Question

In an electron gun, the potential difference between the filament and plate is $3000 \,V$. What will be the velocity of electron emitting from the gun?

• A. $3 \times 10^8 m/s $
• B. $3.18 \times 10^7 m/s $
• C. $3.52 \times 10^7 m/s $
• D. $3.26 \times 10^7 m/s $

Answer 1

Answer: (D)

$V =3000$ volt.
$\frac{1}{2} m v^{2}=e V $
$\Rightarrow v=\frac{\sqrt{2 e V}}{m}$
$\therefore v=\sqrt{\frac{2 \times 1.6 \times 10^{19} \times 3000}{9.1 \times 10^{-31}}}$
$32.6 \times 10^{6}=3.26 \times 10^{7} m / s$