A non-relativistic proton beam passes without deviation through a region of space where there are uniform transverse mutually perpendicular electric and magnetic fields with `E= 120 kVm^-1 and B=50 mT.` Then the beam strikes a grounded target. Find the force which the beam acts on the target if the beam current is equal to `i=0.8 mA`.
Mass of protons `= 1.67xx10^(-27) kg`.

Explanation

Since proton is moving in a straight line hence net force is zero.
`qE = Bqv`
`v = (E)/(B)`
`I = n e rArr n = i//e`
where `n`: number of protons /time.
Momentum of proton `= mv`
Force `F = n m v`
`= (I m E)/(eB)`
`= (0.80 xx 10^(-3) xx 1.67 xx 10^(-27) xx 120 xx 10^(3))/(1.6 xx 10^(-19) xx 50 xx 10^(-3))`
`= 2 xx 10^(-5) N`