Find the force on a negative charge that is placed midway between two equal positive charges. All charges have the same magnitude.

The force on a negative charge that is placed midway between two equal positive charges is zero when all charges have the same magnitude.

Explanation:

Let us assume that

As is the negative charge and placed midway between two equal positive charges ( and ).

Total distance between and is 2r. This means that the distance between and , and = d = r

Now, force action on charge due to is as follows.

where,

k = electrostatic constant =

Substitute the values into above formula as follows.

... (1)

Similarly, force acting on due to is as follows.

  ... (2)

As both the forces represented in equation (1) and (2) are same and equal in magnitude. This means that the net force acting on charge is zero.

Thus, we can conclude that the force on a negative charge that is placed midway between two equal positive charges is zero when all charges have the same magnitude.

increase masses, decrease separation