Practice question

**Electric potential** V = k Q/r, k = 1/(4π ε₀)=9×10⁹ N·m²/C², Q charge (C), r distance (m), scalar, potential at surface of spherical conductor radius R, V = k Q/R. Potential difference ΔV = V_B - V_A = -∫ E·dl, work per unit charge to move charge without acceleration. For r = 0.7 m > R = 0.3 m , E = (1/4 π ε₀) (Q/r²) . E = 9 × 10⁹ × (12 × 10⁻⁸/(0.7)²) = 9 × 10⁹ × (12 × 10⁻⁸/0.49) ≈ 2.204 × 10³ N/C . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq