1.

A beam of fast moving electrons having cross-sectional area A falls normally on a flat surface. The electrons are absorbed by the surface and the average pressure exerted by the electronson this surface is found to be P. If the electrons are moving with a speed v, then the effective current through any cross-section of the electron beam is

Answer»

Ape/(mv)
Ape/`(mv^(2))`
Apv/(me)
Apm/(eV)

Solution :LET N be the average no. of electrons per unit volume, present in the beam of electrons, then impulse momentum THEOREM gives
(NAV)(mv)=F,`P=F/A `
`rArr n=P//(mv^(2))`
`:. i=nAve=(Ape)/(mv)`


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