Question

Two fixed point charges +4uC and +1uc are separated by 30cm in air. Find the position between them at which the resultant electric field is zero or find the neutral point.​

Answer 1

the position at which the the resultant electric field is zero is 10 cm.

• let a be the distance of the position from +1uC and (30-a) be the distance from the +4uC.
• the electric field at this position due to both +1uC and +4uC are equal.

Therefore

                       $\frac{Kq_{1}}{x_{1}^2} =\frac{Kq_{2}}{x_{2}^2} \\Here, q_{1}= +1uC, q_{2}=+4uC, x_{1}=a, x_{2}=(30-a)\\\frac{k*1}{a^2} =\frac{K*4}{(30-a)^2}$

           on Simplifying,

                                    $3a^2+60a-900=0\\\\a =10,-30\\\\a=10 cm$

The neutral point is at 10 cm.