Linear Circuits 1 - 30 - Capacitors, Part 2

Analyze a 2.2-volt source that turns on at t=0 in a simple rc circuit; determine v(0−) = 0 to find the initial capacitor voltage and current.

Determine the capacitor voltage at the instant the source turns on, recognizing that a capacitor's voltage cannot change instantly; since v(0-) is 0 V, v(0+) remains 0 V.

Calculate the capacitor voltage at infinity by treating it as an open circuit and applying voltage division across the 20 ohm and 100 ohm resistors, yielding 367 millivolts.

Explain how the capacitor acts as a short at t=0+ and an open circuit at t→∞, yielding i(0+) ≈ 22 mA and i(∞) = 0 A through the 100-ohm path.

Zero all sources; short the voltage source and open the current source. Treat 100 ohms and 20 ohms in parallel to find tau = RC, 0.167 s.

Choose the voltage and current equations using the initial capacitor values and the decaying exponent, insert the time constant, and obtain the capacitor voltage and current after turn-on.

Analyze a swapped RC circuit with a source, track the capacitor from zero volts to 2.2 volts, and compute the time constant for 20 Ω in parallel with 100 Ω.

Analyze a third resistor-capacitor circuit to find the capacitor voltage over time. Compute the effective resistance and time constant, and describe exponential decay from -10 volts as the capacitor discharges.

This lecture analyzes a resistor-capacitor circuit with a switch, determining the capacitor voltage before and after opening, the time constant, and the exponential decay over time.

Apply simple, reliable processes to find the voltage across a capacitor or the current through a capacitor in any circuit, with no deviations.