Practice question

**Electrostatic shielding** inside hollow conducting shell field zero when no charges inside, regardless of external field, because free charges redistribute on outer surface to cancel external field inside conductor, E=0 inside material in equilibrium, consequence of Gauss's law and conductor property. Work done: W = p E (cos θ₀ - cos θ₁) = 5 × 10⁻⁹ × 2 × 10⁵ × (cos 90° - cos 180°) . W = 5 × 10⁻⁹ × 2 × 10⁵ × (0 - (-1)) = 5 × 10⁻⁹ × 2 × 10⁵ × 1 = 10⁻³ J . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr,