KEAM 2019 Physics and Chemistry Paper

Given, charge q1=+2µC, charge q2=+8µC and distance between the charges d=15cm.
As, the electric field is zero at point p only if the field due to charge +2µC balances the field due to charge +8µC
Let x be the distance from charge q1 at which the electric field is zero as shown in the figure below.∴‌

kq1

x2

=‌

kq2

(15−x)2

⇒‌‌‌

1

x2

=‌

4

(15−x)2

∴‌

1

x

=‌

2

15−x

⇒‌‌2x=15−x
⇒‌‌x=5cm
Thus, the required point is at a distance of 5cm from 2µC.