An 80 μ C charge is given to the 4 μ F capacitor in the circuit shown in the figure so that the upper plate A is positively charged. An unknown resistance R is connected in the left limb. As soon as the switch S in the central limb is closed, a current of 2 A flows through the 2 Ω resistor in the central limb. The capacitive time constant for the circuit is

Step-by-step solution

Potential difference across the central limb = 16 V = Potential difference across 16   Ω = Potential difference across the left limb. ⇒ current through 16 Ω = 1 A ⇒ current through the left limb = 1 A and R = 11   Ω ∴ τ c = 1 6 2 + 2 ohms × 4 × 1 0 - 6   F = 40   μ s