Practice question

**Charge conservation in series** explains same Q: when battery charges first plate, it induces -Q on second plate of same capacitor, which comes from next capacitor's plate, etc., so all have same magnitude Q, potential divides as per 1/C. U = -p E cos θ = -5 × 10⁻⁹ × 3 × 10⁴ × cos 30° . cos 30° = (√(3)/2) ≈ 0.866 , so U = -5 × 10⁻⁹ × 3 × 10⁴ × 0.866 = -1.3 × 10⁻⁴ J . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC parallel, U = ½