Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
Two positive ions, each carrying a charge ' $\mathrm{q}$ ' are separated by a distance ' $\mathrm{d}$ '. If ' $\mathrm{F}$ ' is the force of repulsion between the ions, the number of electrons from each ion will be $(\mathrm{e}=$ charge on electron, $\varepsilon_0=$ permittivity of free space)
PhysicsElectrostaticsJEE Main
Options:
  • A $\sqrt{\frac{4 \pi \varepsilon_0 \mathrm{~d}^2}{\mathrm{e}^2}}$
  • B $\sqrt{\frac{4 \pi \varepsilon_0 \mathrm{Fd}}{\mathrm{e}^2}}$
  • C $\sqrt{\frac{4 \pi \varepsilon_0 \mathrm{Fd}}{\mathrm{e}}}$
  • D $\sqrt{\frac{4 \pi \varepsilon_0 \mathrm{Fd}^2}{\mathrm{e}^2}}$
Solution:
1959 Upvotes Verified Answer
The correct answer is: $\sqrt{\frac{4 \pi \varepsilon_0 \mathrm{Fd}^2}{\mathrm{e}^2}}$
$\begin{aligned} & \mathrm{F}=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{\mathrm{q}^2}{\mathrm{~d}^2}=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{(\mathrm{ne})^2}{\mathrm{~d}^2}=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{\mathrm{n}^2 \mathrm{e}^2}{\mathrm{~d}^2} \\ & \therefore \mathrm{n}=\sqrt{\frac{4 \pi \varepsilon_0 \mathrm{Fd}^2}{\mathrm{e}^2}}\end{aligned}$

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.