Two point charges q1=4uc& q2=9uc are placed 20cm apart.the electric field due to them will be zero on the line joining them at a distance of

8 cm from q1

80/13 cm from q2

80/13 cm from q1

To find the distance at which the electric field due to two point charges is zero on the line joining them, we need to set up an equation using Coulomb's law and solve for distance.

Coulomb's law states that the magnitude of the electric field between two point charges is given by:

E = (k * q1 * q2) / r^2

Where:
E is the electric field,
k is the electrostatic constant (9 × 10^9 Nm^2/C^2),
q1 and q2 are the magnitudes of the charges, and
r is the distance between the charges.

In this case, we are looking for the distance at which the electric field is zero. This means we need to find the distance (r) for which the equation becomes:

0 = (k * q1 * q2) / r^2

We can rearrange the equation to solve for r:

r^2 = (k * q1 * q2) / 0

In this case, the denominator is zero, which means the distance should be infinity for the electric field to become zero. This implies that the electric fields of the two point charges cancel each other out and are balanced at an infinite distance on the line joining them.

Therefore, the electric field due to the two charges will be zero on the line joining them at an infinite distance.

8 cm from q2