HW7solutions

# HW7solutions - Therefore Finally P8.3-6 Before the switch...

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ECE35 Win’09 HW 7 Solutions Chapter 8: 8.3-1, 8.3-3, 8.3-6, 8.3-10, 8.4-6, 8.6-8, 8.6-11. P8.3-1 Here is the circuit before t = 0, when the switch is open and the circuit is at steady state. The open switch is modeled as an open circuit. A capacitor in a steady-state dc circuit acts like an open circuit, so an open circuit replaces the capacitor. The voltage across that open circuit is the initial capacitor voltage, v (0). By voltage division Next, consider the circuit after the switch closes. The closed switch is modeled as a short circuit. We need to find the Thevenin equivalent of the part of the circuit connected to the capacitor. Here’s the circuit used to calculate the open circuit voltage, V oc . Here is the circuit that is used to determine R t . A short circuit has replaced the closed switch. Independent sources are set to zero when calculating R t , so the voltage source has been replaced by a short circuit. Then Finally,

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P8.3-3 Before the switch closes: After the switch closes:

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Unformatted text preview: Therefore . Finally, P8.3-6 Before the switch opens, . After the switch opens the part of the circuit connected to the inductor can be replaced by it's Norton equivalent circuit to get: Therefore . Next, Finally , P8.3-10 First, use source transformations to obtain the equivalent circuit for t < 0: for t > 0: P8.4-6 , and P8.6-8 For t < 0, the circuit is: After t = 0, replace the part of the circuit connected to the capacitor by its Thevenin equivalent circuit to get: P8.6-11 For t > 0 the circuit is at steady state so the inductor acts like a short circuit: Apply KVL to the supermesh corresponding to the dependent source to get Apply KVL to get so and (a) For t > 0, find the Norton equivalent circuit for the part of the circuit that is connected to the inductor. Apply KCL at the top node of the dependent source to see that . Then Apply KVL to the supermesh corresponding to the dependent source to get Apply KCL to get Then Then , so and now...
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HW7solutions - Therefore Finally P8.3-6 Before the switch...

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