The potential difference between the plates of a flat air condenser is 150 V. The area of each plate is 120 cm²

The potential difference between the plates of a flat air condenser is 150 V. The area of each plate is 120 cm², and the charge is 5 nC. What is the distance between the plates.

These tasks: φ1 – φ2 (potential difference between the plates) = 150 V = U (voltage); S (area of each plate) = 120 cm2 = 0.012 m2; q (charge) = 5 nC = 5 * 10-9 C.

Constants: ε (dielectric constant of air) = 1; ε0 (electrical constant) = 8.85 * 10-12 C2 / (N * m2).

To calculate the distance between the plates, we use the equality: q / U = C = ε * ε0 * S / d, whence d = ε * ε0 * S * U / q.

Calculation: d = 1 * 8.85 * 10-12 * 0.012 * 150 / (5 * 10-9) = 0.003186 m or 3.186 mm.