Question

A point charge $$Q_1$$ exerts some force on a second point charge $$Q_2$$. If a 3rd point charge $$Q_3$$ is brought near, the force of $$Q_1$$ exerted on $$Q_2$$ (without changing their respective positions):
A. Will increase
B. Will decrease
C. Will remain unchanged
D. Will increases if $$Q_3$$ is of same sign as $$Q_1$$ and will decrease if $$Q_3$$ is of opposite sign

Answer 1

Hint:Remember the principle of superposition of the electric charges. Also consider the effect of presence of a new electric charge on the electrostatic force between the two initial electric charges.

Complete step by step answer:
According to the principle of superposition of the charges, the net force exerted by a number of charges on a point charge is the sum of the individual forces exerted by all the charges on the point charge.Also, the individual force exerted by one of these charges on some other point charge is independent of the presence of the other charges.A point charge $$Q_1$$ exerts some force on a second point charge $$Q_2$$. If a 3rd point charge $$Q_3$$ is brought to near the point charge $$Q_1$$, the force of point charge $$Q_1$$ exerted on a second point $$Q_2$$ charge will remain the same according to the principle of superposition of the charges.However, the net force on second point charge $$Q_2$$ due to the charges $$Q_1$$ and $$Q_3$$ will definitely change.
Hence, the force of point charge $$Q_1$$ exerted on a second point $$Q_2$$ charge will not be affected by the presence of a third point charge $$Q_3$$.

Note:The net force of point charge $$Q_1$$ exerted on a second point $$Q_2$$ charge will change due to point charge $$Q_3$$ but the individual force of point charge $$Q_1$$ exerted on a second point $$Q_2$$ charge will remain the same.