Coulomb’s Law

Physics ⇒ Electricity and Magnetism

Coulomb’s Law starts at 9 and continues till grade 12. QuestionsToday has an evolving set of questions to continuously challenge students so that their knowledge grows in Coulomb’s Law. How you perform is determined by your score and the time you take. When you play a quiz, your answers are evaluated in concept instead of actual words and definitions used.

See sample questions for grade 12

Calculate the force between two charges of +2 μC and -3 μC placed 0.5 m apart in vacuum. (Take k = 9 × 10⁹ N·m²/C²)

Calculate the force between two charges of 1 C each placed 1 m apart in air. (k = 9 × 10⁹ N·m²/C²)

Describe how the force between two charges changes if both charges are tripled and the distance between them is doubled.

Describe the effect of the sign of charges on the direction of the force according to Coulomb’s Law.

Describe the superposition principle as it applies to electrostatic forces.

Explain the significance of the inverse square nature of Coulomb’s Law.

Explain why Coulomb’s Law is not applicable for extended bodies with non-uniform charge distribution.

If the electrostatic force between two charges is 5 N in air, what will it be in a medium with ε_r = 10?

If the force between two charges is F in air, what will be the force between them in a medium of relative permittivity 5?

If the magnitude of each of two point charges is doubled and the distance between them is halved, by what factor does the force change?

If three charges are placed at the vertices of an equilateral triangle, explain how to find the net force on one of the charges.

State Coulomb’s Law and write its mathematical expression.

The force between two charges is 10 N. If the distance between them is increased by a factor of 3, what is the new force?

Two charges +q and -q are placed 10 cm apart. What is the nature of the force between them?

Two charges, +4 μC and +6 μC, are placed 0.2 m apart in a medium with ε_r = 2. Calculate the force between them. (k = 9 × 10⁹ N·m²/C²)

A charge of +2 μC is placed at the origin, and a charge of -3 μC is placed at (0, 4 cm). A third charge of +4 μC is placed at (3 cm, 0). Calculate the net force (magnitude and direction) on the +4 μC charge. (k = 9 × 10⁹ N·m²/C²)

A point charge q is placed at the center of a cube. What is the net electrostatic force experienced by the charge due to the induced charges on the surface of the cube?

A proton and an electron are separated by a distance r. Compare the magnitude of the electrostatic force between them to the gravitational force between them. Which is stronger and by approximately what factor?

Derive the expression for the force between two point charges embedded in a medium of relative permittivity ε_r, and explain how the force changes as ε_r increases.

Suppose the electrostatic force between two charges is F in vacuum. If a dielectric slab of thickness equal to half the distance between the charges and relative permittivity ε_r is inserted between them, what will be the new force?