Question

Through a given cross section n, electrons per second are passing from left to right and n, protons nem
are passing from right to left simultaneously. The electric current through that cross section is (e = sle
charge)
(1) (n1 + n2)e toward left
(2) (n2 - n1)e toward right
(3) (n1*2 + n2*2)e toward left
(4) (n2*2 - n1*2)e toward right ​

Answer 1

Given:

Through a given cross section n1 electrons per second are passing from left to right and n2 protons are passing from right to left simultaneously.

To find:

Net current through that cross section.

Calculation:

Current is given as the instantaneous rate of flow of charges ; the direction of current is always in the direction of movements of protons and opposite to that of electrons.

N is number of particles , n is number of particles per second.

$\rm{ \therefore \: I = \dfrac{dq}{dt} }$

$\rm{ = > \: I = \dfrac{d \bigg \{(N1)e + (N2)e \bigg \}}{dt} }$

$\rm{ = > \: I = \dfrac{d \bigg \{(N1 + N2)e \bigg \}}{dt} }$

$\rm{ = > \: I =e \dfrac{d (N1 )}{dt} } + e \dfrac{d(N2)}{dt}$

$\rm{ = > \: I =e (n1) + e (n2)}$

$\rm{ = > \: I = (n1 + n2)e}$

So, final answer is:

$\boxed{ \boxed{ \rm\: I = (n1 + n2)e} \: \rm \: towards \: left}$

Answer 2

Answer:

option (1) (n1+n2)e towards left