How does Coulomb's Law compare to Newton's Law of Gravitation?

Both are inverse-square laws: F ∝ 1/r². Both are central forces acting along the line joining two bodies. Differences: (1) Gravitational force is always attractive; Coulomb force can be attractive or repulsive. (2) Coulomb force is ~10³⁶ times stronger than gravitational force. (3) Coulomb force depends on medium (εᵣ); gravitational force does not.

What is the electric field inside a hollow conductor?

The electric field inside a hollow conductor is zero. All free charges reside only on the outer surface. This is the principle of electrostatic shielding — a Faraday cage. Applications: metal-lined aircraft/cars protect passengers from lightning; coaxial cables shield signals from external interference.

State Gauss's Law and give one application.

Gauss's Law: The net electric flux through any closed surface = q_enclosed/ε₀. Application: Finding E due to an infinite uniformly charged sheet (charge density σ). Using a cylindrical Gaussian surface: 2E·A = σA/ε₀ → E = σ/(2ε₀). This is independent of distance from the sheet — a uniform electric field.

Coulomb's Law and Electric Field

Electric Charges and Fields • Class 12 Physics • NCERT • CBSE

Coulomb's Law: F = kq₁q₂/r² where k = 9×10⁹ N m² C⁻². Electric field E = F/q = kq/r² (N/C). Electric dipole moment p = q×2l. Gauss's Theorem: Total electric flux through a closed surface = q_enclosed/ε₀.

Key Formulas

F = kq₁q₂/r² (k = 9×10⁹ N m² C⁻²)
E = kq/r²
Dipole moment p = q·2l
Gauss's Law: Φ = q_enclosed/ε₀
E (infinite sheet) = σ/(2ε₀)

Frequently Asked Questions

How does Coulomb's Law compare to Newton's Law of Gravitation?: Both are inverse-square laws: F ∝ 1/r². Both are central forces acting along the line joining two bodies. Differences: (1) Gravitational force is always attractive; Coulomb force can be attractive or repulsive. (2) Coulomb force is ~10³⁶ times stronger than gravitational force. (3) Coulomb force depends on medium (εᵣ); gravitational force does not.
What is the electric field inside a hollow conductor?: The electric field inside a hollow conductor is zero. All free charges reside only on the outer surface. This is the principle of electrostatic shielding — a Faraday cage. Applications: metal-lined aircraft/cars protect passengers from lightning; coaxial cables shield signals from external interference.
State Gauss's Law and give one application.: Gauss's Law: The net electric flux through any closed surface = q_enclosed/ε₀. Application: Finding E due to an infinite uniformly charged sheet (charge density σ). Using a cylindrical Gaussian surface: 2E·A = σA/ε₀ → E = σ/(2ε₀). This is independent of distance from the sheet — a uniform electric field.

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