In a medium the force of attraction between two point electric charges, distance d apart, is F. What distance apart should these be kept in the same medium so that the force between them becomes (i) 3 F (ii) F / 3?

Solution

Let q₁and q₂be the point charges. Then, force between the charges when kept at a distance 'd' apart is given by

$F = \frac{1}{4 {πε}_{\circ}} \frac{q_{1} q_{2}}{d^{2}}$

a) Suppose that the force between two charges becomes 3F when kept at a distance 'x' apart
$i . e, \frac{1}{4 {πε}_{\circ}} \frac{q_{1} q_{2}}{x^{2}} = 3 [\frac{1}{4 {πε}_{\circ}} \frac{q_{1} q_{2}}{d^{2}}] \Rightarrow x^{2} = \frac{d^{2}}{3} \Rightarrow x = \pm \frac{d}{\sqrt{3}}$
b) Suppose that the force between two charges becomes F/3 when kept at distance 'x' apart.

$i . e, \frac{1}{4 {πε}_{\circ}} \frac{q_{1} q_{2}}{x^{2}} = \frac{1}{3} [\frac{1}{4 {πε}_{\circ}} \frac{q_{1} q_{2}}{d^{2}}] \Rightarrow x^{2} = 3 d^{2} \Rightarrow x = \pm \sqrt{3} d$

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Electric Charges And Fields

In a medium the force of attraction between two point electric charges, distance d apart, is F. What distance apart should these be kept in the same medium so that the force between them becomes (i) 3 F (ii) F / 3?

Some More Questions From Electric Charges and Fields Chapter

a) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?
b) Explain why two field lines never cross each other at any point?

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For Daily Free Study Material Join wiredfaculty

Electric Charges And Fields

In a medium the force of attraction between two point electric charges, distance d apart, is F. What distance apart should these be kept in the same medium so that the force between them becomes (i) 3 F (ii) F / 3?

Some More Questions From Electric Charges and Fields Chapter

a) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?b) Explain why two field lines never cross each other at any point?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

a) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?
b) Explain why two field lines never cross each other at any point?