Electrostatic Potential And Capacitance

Question

A charged particle is accelerated by a potential of 200 V. If its velocity is 8.4 × 10⁸ m/s, then value of e/m for that particle is

17.6 × 10¹⁶

14.5 × 10¹²

1.76 × 10¹⁵

1.45 × 10¹⁵

Solution

1.76 × 10¹⁵

If electron is accelerated by voltage V, then its kinetic energy

$\frac{1}{2} m v^{2}$ = qV

Where V is the velocity of accelerated particles

q is the charge on particle

m is the mass

⇒ $\frac{q}{m} = \frac{v^{2}}{2 V}$

= $\frac{(8.4 \times 10^{8})}{2 \times 200}$

$\frac{q}{m}$ = 1.76 × 10¹⁵