Question

consider a system of 3-point charges on the x-axis. Charge 1 is at x=0, charge 2 at x=0.2m, and charge 3 is at x = 0.4m. Charge 1 = -19microC and charge 2=3=+19microC.

a) at some point the electric field vanishes on the x axis between 0.2 and 0.4. Find that point.

b) there is another point that the e field is also 0. Find it!

Answer 1

(a) scince the three charges are equal inmgnetude , if the only q1 and q2 is present then the

field is zero at middle point of q2 and q3 thatis at x = (0.2+0.4)/2 = 0.30 m from the origin . if we consider the

three charges then the electiric field is zero at the point left of the x = 0.30m

(b)

at the point of zero electric field the field due tocharge q1 and q3 acts left wards and due to

     charge q2 right .

         Let xbe the distance between the zero electric field and x-axis

     then 0 = - Kq/x²  + Kq/(0.40m-x)² + Kq/(x-0.20m)²

x = - 0.688 m