Physics

Problem

Two point charges

q_1

and

q_2

are kept fixed in vacuum on a straight line with a separation

d

. A point

P

is located along the same line at a distance

x

from

q_1

(measured towards

q_2

). a. (i) Derive an expression for

x

in terms of

d

q_1

, and

q_2

for which the electric field at

P

is zero. b. (ii) Using your result, show that when

q_1=q_2

no finite point of zero electric field exists on the line. c. (iii) If

q_1=9q_2

, express

x

as a fraction of

d

and state on which side of the line segment (inside it or outside it) the null point is situated.