In Millikan’s oil drop experiment, an oil drop of mass $16 \times {10^{ - 6}}kg$ is balanced by an electric field of ${10^6}V/m.$ The charge in coulomb on the drop, assuming $g = 10\,m/{s^2}$ is

In a Thomson set-up for the determination of e/m, electrons accelerated by $2.5$ $kV$ enter the region of crossed electric and magnetic fields of strengths $3.6 \times {10^4}V{m^{ - 1}}$ and $1.2 \times {10^{ - 3}}T$ respectively and go through undeflected. The measured value of $e/m$ of the electron is equal to

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

What is specific charge ? Write its standard value.

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

In $1897$, J.J.Thomson invented which particle ?