Question

Two point charges 20 microcoloumb and 80 micocoloumb are placed 18 cm apart. Find the position where the electric field is zero?

Answer 1

Answer:

The electric filed is zero at 6 cm from 20 micro coulomb charge.

Explanation:

Given that,

First point charge $q_{1}= 20\times10^{-6}$

Second point charge $q_{2}= 80\times10^{-6}$

Distance d = 18 cm

let x cm from 20 micro coulomb electric field would be zero.

According to the formula,

The electric field from a point charge 20 micro coulomb at point C.

$E_{1}=\dfrac{k\timex 20\times 10^{-6}}{x^2}$

The electric field from a point charge 80 micro coulomb at point C.

$E_{2}=\dfrac{k\timex 80\times 10^{-6}}{(18-x)^2}$

Net electric field at point C is zero

Thus, $E_1=E_2$

$\dfrac{k\timex 20\times 10^{-6}}{x^2}=\dfrac{k\timex 80\times 10^{-6}}{(18-x)^2}$

$\dfrac{1}{x^2}=\dfrac{4}{(18-x)^2}$

$18-x=2x$

$x=6$

Hence, The electric filed is zero at 6 cm from 20 micro coulomb charge.