Question

An infinite number of charges, each equal to 2 u
are placed along y-axis at y = 1 m, 2 m, 4 m
The electric field intensity at the origin is
(1) 2.4 * 10' N/C (2) 2.4 x 10- N/C
(3) 1.2 x 10' N/C (4) 0.57 × 10-N/C
si dinole is placed in uniform electric field​

Answer 1

Given

q=2u

placed along y-axis at y=1,y=2,y=4,y=8...............

now the electric field intensity at origin O is

E=Kq/r^2 where K=9 x 10^9

E=Kq/1^2 +Kq/2^2+ kq/4^2 +..........

E=Kq/1+Kq/4+Kq/16+Kq/64.........................

E=Kq(1+1/4+1/16+1/64+....................)

E=Kq(1/1-1/4)

E=9 x 10^9 x2u (1/3/4)

E=9 x10 ^9 x 2u x 4/3          (or) E=K8u/3

E=24 x 10^9