Question

Two point like charges $Q_1$ and $Q_2$ of whose strength are equal in absolute value are placed at a certain distance from each other. Assuming the field strength to be positive in the positive direction of x-axis the signs of the charges $Q_1$ and $Q_2$ for the graphs (field strength versus distance) shown in Figures $1,2,3$ and $4$ are

• A. $Q_{1}$ positive, $Q_{2}$ negative; both positive; $Q_{1}$ negative, $Q_{2}$ positive; both negative
• B. $Q_{1}$ negative $Q_{2}$ positive; $Q_{1}$ positive, $Q_{2}$ negative; both positive; both negative
• C. $Q_{1}$ positive, $Q_{2}$ negative; both negative; $Q_{1}$ negative, $Q_{2}$ positive; both positive
• D. both positive; $Q_{1}$ positive, $Q_{2}$ negative $; Q_{1}$ negative, $Q_{2}$ positive; both negative

Answer 1

Answer: (D)

For a point charge, $E \propto \frac{1}{X^{2}}$. For positive charges, electric field will decrease in positive direction as distance increases, (case 1), for negative charge, as distance increases field will increase (case 4). As we move from positive charge to negative charge, field will keep on decreasing (case 2), As we move from negative to positive charge, field will keep on increasing (case 3)