In a Millikan's oil drop experiment the charge on an oil drop is calculated to be $6.35 \times {10^{ - 19}}C$. The number of excess electrons on the drop is

An electron of charge $‘e’$ coulomb passes through a potential difference of $V$ volts. Its energy in ‘joules’ will be

An electron gun with its collector at a potential of $100\; V$ fires out electrons in a spherical bulb containing hydrogen gas at low pressure $(\sim 10^{-2} \;mm$ of $Hg$ . A magnetic field of $2.83 \times 10^{-4}\; T$ curves the path of the electrons in a circular orbit of radius $12.0 \;cm .$ (The path can be viewed because the gas tons in the path focus the beam by attracting electrons, and emitting light by electron capture; this method is known as the 'fine beam tube' method.) Determine $e / m$ from the data.

Electron volt is a unit of

Which of the following is not the property of a cathode ray

In a parabola spectrograph, the velocities of four positive ions $P,Q,R$ and $S$ are $v_1$, $v_2$, $v_3$ and $v_4$ respectively