Question

Charge -q and +q located at A and B, respectively, constitute an electric dipole. Distance AB = 2a, O is the mid point of the dipole and OP is perpendicular to AB. A charge Q is placed at P where OP = y and y >> 2a. The charge Q experiences and electrostatic force F. If Q is now moved along the equatorial line to P' such that $O{P}^{\prime }=\left(\frac{y}{3}\right)$ the force on Q will be close to L : $(\frac{y}{3}>>2a)$

• A. $\frac{F}{3}$
• B. 3F
• C. 9F
• D. 27 F

Answer 1

Answer: (D)

27 F

$F_A=\frac{kP}{y^3}Q=F$

$F_B=E_B\times Q$

$F_B=\frac{kP}{y^3}\cdot (3{)}^3\cdot Q$

$=27\times F_A$ $\to 27F$.