An electron beam is moving between two parallel plates having electric field $1.125 \times {10^{ - 6}}N/m$. A magnetic field $3 \times {10^{ - 10}}T$ is also applied so that beam of electrons do not deflect. The velocity of the electron is ............ $m/s$

In Millikan's experiment for the determination of the charge on the electron, the reason for using the oil is

Write and explain methods to obtain emission of electron from metal.

A cathode emits $1.8 \times {10^{14}}$ electrons per second, when heated. When $ 400\;V$  is applied to anode all the emitted electrons reach the anode. The charge on electron is $1.6 \times {10^{ - 19}}\;C$. The maximum anode current is ............ $\mu A$

Kinetic energy of emitted cathode rays is dependent on

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