In Fig.1.1, two positive charges q2 and q3 fixed along the y axis, exert a net electric force in the + x direction on a charge q1 fixed along the x axis. If a positive charge Q is added at (x, 0), the force on q1


It is given that q2 and q3 are positive charges. The charge on the q1 is not given and it may be positive or negative charge. It also given that net force on the charge q1 is directed along positive x direction.


If we consider q1 as positive charge, then by coulomb’s law, the net electric force will be in negative direction as shown in the figure below. However, this will be not the case according to the given data. Therefore, charge q1 is negative charged and the resultant electric force FR, in positive x direction is shown below.



Now, the positive charge Q is placed at the given point. This causes the exertion of electric force FQ on charge q1. This force FQ is also directed along positive x axis due to Coulomb’s law. Hence the force on charge q1 is increased. The resultant force FR+ FQ is shown in the figure below



Thus, the force on given charge is increased along positive x axis.

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