For an RC circuit with R = 1 kΩ and C = 1 μF, what is the time constant τ?

For an RC circuit with R = 1 kΩ and C = 1 μF, what is the time constant τ?

• A. 0.5 ms
• B. 2 ms
• C. 1 ms
• D. 10 ms

Answer: (C)

The time constant of an RC circuit is RC, which dictates how quickly the capacitor charges or discharges after a step. With R = 1 kΩ (1000 Ω) and C = 1 μF (1×10^-6 F), tau = RC = 1000 × 1×10^-6 = 1×10^-3 seconds = 1 ms. So the time constant is 1 ms. After one tau, the capacitor reaches about 63% of its final value, and after five taus, about 99%.

The time constant of an RC circuit is RC, which dictates how quickly the capacitor charges or discharges after a step. With R = 1 kΩ (1000 Ω) and C = 1 μF (1×10^-6 F), tau = RC = 1000 × 1×10^-6 = 1×10^-3 seconds = 1 ms. So the time constant is 1 ms. After one tau, the capacitor reaches about 63% of its final value, and after five taus, about 99%.