Final answer:
To find the time constant of the circuit, we can use the formula RC, where R is the total resistance and C is the capacitance. In this case, the total resistance is 205Ω and the capacitance is 0.25μF. Therefore, the time constant is 51.25μs.
Step-by-step explanation:
In the given question, a 0.25μF capacitor is initially charged to 70 V. It is then connected in series with a 55Ω resistor and a 150Ω resistor and allowed to discharge completely. To find the time constant of the circuit, we can use the formula RC, where R is the total resistance and C is the capacitance. In this case, the total resistance is the sum of the two resistors, which is 205Ω, and the capacitance is 0.25μF. Therefore, the time constant is 205Ω * 0.25μF = 51.25μs.