Question

A few electric field lines for a system of two charges $Q_1$ and $Q_2$ fixed at two different points on the $x-axis$ are shown in the figure. These lines suggest that

• A. $|Q_1| > |Q_2|$
• B. $|Q_1| < |Q_2|$
• C. at a finite distance to the left of $Q_1$ the electric field is zero
• D. at a finite distance to the right of $Q_2$ the electric field is
  zero

Answer 1

Answer: (A), (D)

From the behaviour of electric lines, we can say that $Q_1$ is positive and $Q_2$ is negative. Further, $|Q_1| > |Q_2|$
At some finite distance to the right of $Q_2$, electric field will be zero. Because electric field due to $Q_1$ is towards right (away from $Q_1$ ) and due to $Q_2$ is towards left (towards $Q_2$). But since magnitude of $Q_1$ is more, the two fields may cancel each other because distance of that point from $Q_1$ will also be more.
$\therefore $ The correct options are (a) and (d).