Question 63Electricity & Electronics - 1st Asst/Chief

The correct answer is B) 3 seconds. The time constant (τ) for a series RC circuit is calculated as τ = R * C, where R is the resistance in ohms and C is the capacitance in farads. Given the values of R1 = 3 megohms and C1 = 1 microfarad, the time constant is τ = 3 megohms * 1 microfarad = 3 seconds. The other options are incorrect because 0.33 seconds is less than the time constant, 6 seconds is twice the time constant, and 15 seconds is five times the time constant.