Exams › NEET › Physics

Two equal charges are separated by a distance $d$. A third charge placed on the perpendicular bisector at a distance $x$ from the midpoint will experience maximum Coulomb force when

1. $x=d/2$
2. $x=d$
3. $x=d/\sqrt{2}$
4. $x=3d/2$

Correct answer: $x=d/\sqrt{2}$

Solution

The net force on the third charge is along the perpendicular bisector. Its magnitude is proportional to $x/(x^2+d^2/4)^{3/2}$, which is maximized by differentiation. This gives $x=d/\sqrt{2}$.

Related NEET Physics questions

• Which of the following statements is not true about Gauss's law?
• A positive charge and a negative charge are held in place and initially form a dipole. Then a uncharged conducting bar is placed in between them. How is the force between the charges affected?
• The capacitance of a parallel-plate capacitor is 10 μF without the dielectric. A material with dielectric constant 2 is used to fill half the thickness between the plates. The new capacitance is:
• A point charge is brought in an electric field. The electric field at a nearby point: This question has multiple correct options
• Assertion A capacitor can be given only a limited quantity of charge Reason A capacitor is an arrangement which can store sufficient quantity of charge
• A soap bubble of radius 3 cm is charged with surface charge density σ such that (σ²)/(ε₀)=0.4 S I units. The excess pressure inside the bubble in SI unit (surface tension of soap solution =3 × 10⁻³ N / m) is:

⚔️ Practice NEET Physics free + battle 1v1 →