Question:medium

Two point charges \(+2 \, \mu\text{C}\) and \(-2 \, \mu\text{C}\) are placed 0.1 m apart in air. What is the electrostatic force between them?

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Always convert microcoulombs (\( \mu\text{C} \)) to coulombs (\( \text{C} \)) before using Coulomb’s Law.
Updated On: Nov 26, 2025
  • \(3.6 \, \text{N}\)
  • \(1.8 \, \text{N}\)
  • \(4.2 \, \text{N}\)
  • \(0.72 \, \text{N}\)
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The Correct Option is A

Solution and Explanation

Given: - Charge \(q_1 = +2 \times 10^{-6} \, \text{C}\) - Charge \(q_2 = -2 \times 10^{-6} \, \text{C}\) - Distance \(r = 0.1 \, \text{m}\) - Coulomb's constant \(k = 9 \times 10^9 \, \text{Nm}^2/\text{C}^2\) Step 1: Calculate the magnitude of the electrostatic force using Coulomb's Law \[ F = \frac{k |q_1 q_2|}{r^2} \] \[ F = \frac{(9 \times 10^9) \cdot |(2 \times 10^{-6}) \cdot (-2 \times 10^{-6})|}{(0.1)^2} \] \[ F = \frac{9 \times 10^9 \cdot (4 \times 10^{-12})}{0.01} = \frac{36 \times 10^{-3}}{0.01} = 3.6 \, \text{N} \] Step 2: Determine the direction of the force The charges have opposite signs, indicating an attractive force. Answer: The electrostatic force between the charges is \(3.6 \, \text{N}\). This corresponds to option (1).
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