Question

In a ionic liquid, electric currents are carried by both positive and negative ions. An electric field is set up in a cylinder of cross-sectional area A. Positive ions drift to the left with speed v1 and negative charges drift to the right with speed v2. The liquid is neutral so the density of positive and negative charge carriers are both equal to n. The positive ions have charge +e and the negative ions have charge -e. What is the current?

Group of answer choices

I = e n A v1 + e n A v2 to the right

I = e n A v1 - e n A v2 to the left

I = e n A v1 + e n A v2 to the left

I = e n A v1 - e n A v2 to the right

Answer 1

We know that the direction of current is along the direction of flow of positive charge and opposite to flow of negative charge . So , obviously the directions of current due to both positive and negative charge are to the left .

Given charge density = n . Cross-section of cylinder= A

Velocity = v (distance per unit time) then number of charge passing the volume= Av per unit time is nAv . So , amount of charge per unit time i.e Current (I) is = enAv.

Thus for both positive and negative charge total current , I = enAV1+ enAV2 , to the left