Q: 1 st Order Circuits: Find τ, Initial Value v 0 or i 0 , Final Value v ∞ or i ∞ 1. Find τ Find the R Th for the 1 st order circuit at t > 0 ● Turn off all the Sources Voltage Source → Short Circuit (Wire) Current Source → Open Circuit (Removed Wire) ● Remove the Energy Storing Device (Capacitor or Inductor) Replace by a pair of Terminals ● Determine the Resistance at the Terminals (Start with inner most resistors) Resistors in Series → Current can only flow one path between them Resistors in Parallel → End Terminals connect to the same nodes Calculate τ ● For a 1 st order RC circuit: τ = R Th C ● For a 1 st order RL circuit: τ = L R Th Note: Any resistor in parallel with a “Wire” has a resistance of 0 . (“Shorted” Resistor) Any resistor in series with an Open Circuit (Removed Wire) has a resistance of 0 . (“No Effect”) 2. Find Initial Value v 0 or i 0 Step 1 First thing you need to determine is the Capacitor Voltage
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