Question

In the given figure, two positive charges $q_2\text{and}{q}_3$ 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 \

• A. shall increase but the direction changes because of the intersection of $Q\text{with}{q}_2\text{and}{q}_3$.
• B. shall point along the negative $x-axis$
• C. shall increase along the positive $x-axis$.
• D. shall decrease along the positive $x-axis$.

Answer 1

The correct option is C

shall increase along the positive $x-axis$.

As we know that like charges repel and unlike charges attract.
In the given figure $\left(a\right)$, the net electrostatic force on the charge $q_1$ by the charges $q_2\text{and}{q}_3$ is along the positive $x-direction$. Hence the nature of force between $q_1,q_2\text{and}{q}_1,q_3$ should be attractive. This shows $q_1$ should be negative.



In the figure $\left(b\right)$, a positive charge $Q$ is placed at $(x,0)$, hence the nature of force between $q_1\text{and}Q\left(\text{positive}\right)$ will be attractive and the force on $q_1$ by the charge $Q$ should be along positive $x-axis\text{direction}$.
Therefore, due to addition of positive charge $Q\text{at}(x,0)$, the force on $q_1$ shall increase along the positive $X-axis$.
Final Answer: $\left(a\right)$