Question

In figure, two positive charges, $q_2$ and $q_3$ fixed along the $y$ axis, exert a net electric force in the $+x$ direction on a charge $q_1$ fixed along the $x$ axis. If a positive charge Q is added at ($x$, $0$), the force on $q_1$

• A. shall increase along the positive $x$-axis
• B. shall decrease along the positive $x$-axis
• C. shall point along the negative $x$-axis
• D. shall increase but the direction changes because of the intersection of $Q$ with $q_2$ and $q_3$

Answer 1

Answer: (A)

shall increase along the positive $x$-axis

Answer 2

Since positive charge $q_2$ and $q_3$ exert a net force in the $+ X$-direction on the charge $q_1$ fixed along the $X$-axis, the charge $q_1$ is negative as shown in figure. Obviously, due to addition of positive charge $Q$ at ($x$,$0$), the force on $-q$ shall increase along the positive $X$-axis.