In Milikan’s experiment, an oil drop having charge $q$ gets stationary on applying a potential difference $V$ in between two plates separated by a distance $‘d’$. The weight of the drop is

In Bainbridge mass spectrograph a potential difference of $1000 V$ is applied between two plates distant $1$ cm apart and magnetic field in $B = 1T$. The velocity of undeflected positive ions in m/s from the velocity selector is

A narrow electron beam passes undeviated through an electric field $E = 3 \times {10^4}volt/m$ and an overlapping magnetic field $B = 2 \times {10^{ - 3}}Weber/{m^2}$. If electric field and magnetic field are mutually perpendicular. The speed of the electrons is

$n$ Millikan oil drop experiment, a charged drop of mass $1.8 \times {10^{ - 14}}kg $ is stationary between its plates. The distance between its plates is $0.90 cm$ and potential difference is $2.0$ kilo volts. The number of electrons on the drop is

Three particles having their charges in the ratio of $1 : 3 : 5$ produce the same spot on the screen in Thomson’s experiment. Their masses are in the ratio of

An electron initially at rest, is accelerated through a potential difference of $ 200$  volt, so that it acquires a velocity $8.4 \times {10^6}m/s.$ The value of $e/m$ of electron will be