JEE PYQ: Electrostatics Question 56
Question 56 - 2019 (10 Jan Shift 2)
Charges $-q$ 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 $y \gg 2a$. The charge $Q$ experiences an electrostatic force $F$. If $Q$ is now moved along the equatorial line to $P’$ such that $OP’ = \frac{y}{3}$, ($\frac{y}{3} \gg 2a$), the force on $Q$ will be close to:
(1) $3F$
(2) $\frac{F}{3}$
(3) $9F$
(4) $27F$
Show Answer
Answer: (4)
Solution
On the equatorial line, $F \propto \frac{1}{r^3}$. When distance changes from $y$ to $y/3$: $F’ = F \times \left(\frac{y}{y/3}\right)^3 = 27F$.
BETA
