In Millikan's experiment for the determination of the charge on the electron, the reason for using the oil is
It is a lubricant
Its density is higher
It vapourises easily
It does not vapourise
An $\alpha$ particle is accelerated through a p.d of ${10^6}$ volt then $ K.E$ . of particle will be .......... $MeV$
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 ............ $\mu A$
In the Millikan's experiment, the distance between two horizontal plates is $2.5 \,\,cm$ and the potential difference applied is $250\,\, V$ . The electric field between the plates will be ....... $V/m$
A metal plate gets heated, when cathode rays strike against, it due to
In $1897$, J.J.Thomson invented which particle ?