A free pith ball of mass 8 g carries a positive charge of 5 x 10^–8 C. What must be the nature and magnitude of charge that should be given to a second pith ball fixed 5 cm vertically below the former pith ball so that the upper pith ball is stationary?

Solution

The question ca be depicted using a fig. as mentioned below.

Let m be the mass of the upper pith ball. Let q₁ represent the charge on the upper ball. For equilibrium to be maintained for upper ball, it must experience an upward electric force F_e. This is possible if the lower ball has positive charge, say, q₂.

For equilibrium,

\frac{1}{4 {πε}_{0}} \frac{q_{1} q_{2}}{r^{2}} = mg

Substituting values,

\frac{9 \times 10^{9} \times 5 \times 10^{- 8} \times q_{2}}{(5 \times 10^{- 2})^{2}} = 8 \times 10^{- 3} \times 9.8

\Rightarrow

q_{2} = 4.356 \times 10^{- 7} C

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Electric Charges And Fields

A free pith ball of mass 8 g carries a positive charge of 5 x 10^–8 C. What must be the nature and magnitude of charge that should be given to a second pith ball fixed 5 cm vertically below the former pith ball so that the upper pith ball is stationary?

Some More Questions From Electric Charges and Fields Chapter

Figure shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?

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Electric Charges And Fields

A free pith ball of mass 8 g carries a positive charge of 5 x 10–8 C. What must be the nature and magnitude of charge that should be given to a second pith ball fixed 5 cm vertically below the former pith ball so that the upper pith ball is stationary?

Some More Questions From Electric Charges and Fields Chapter

Figure shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

A free pith ball of mass 8 g carries a positive charge of 5 x 10^–8 C. What must be the nature and magnitude of charge that should be given to a second pith ball fixed 5 cm vertically below the former pith ball so that the upper pith ball is stationary?