Find the total linear momentum of the electrons in a conductor of length `l = 1000m` carrying a current `I = 70A`.

Answer

4

Explanation

Let a be the area of the cross-section of the wire and `n` be the number density of electrons in the wire. If `N` is the total no of electron crossing per second through a cross section of wire due to current `I` flowing then
`N = (1)/(e ) = n a l or I = n a l e`.....(i)
But `I = n a e upsilon_(d) or upsilon_(d) = (1)/(n a e)= ( na l e )/(n a e) = l`
Total momentum of electrons in the stringht wire
is `= Nm upsilon_(d) = (1)/(e ) xx mxxl = (70 xx (9xx 10^(-31)) xx 1000)/(16 xx 10^(-19))`
`~~ 4 xx 10^(-7) Ns`.