ELEC 105, Spring 2004
Prof. Rich Kozick

## Homework 6

Date Assigned: Friday, March 5, 2004
Date Due: Friday, March 12, 2004

1. Reading: In the Hambley text, please read Chapter 3, Sections 3.1-3.4 on capacitors, and also read Chapter 4, Sections 4.1 and 4.2, on RC circuits.

We will study inductors and RL circuits next, which are in Sections 3.4-3.6 and 4.3. Then we will study filters (portions of Chapters 5 and 6).

2. Please solve the following problems at the end of Chapters 3 and 4 in the Hambley text.
Chapter 3: 3.9 and 3.15.
Chapter 4: 4.5 (what is the time constant in this circuit?).

3. Please analyze the RC circuit that we used in Lab 6 for the following cases. Assume that Vs = 12 V, C = 1 microfarad, R = 1,000 ohms, and Rs = 100 ohms.
• Assume that the switch was closed for a long time, and that it is opened at time t=0. Find the expression for v(t) and make a sketch of the voltage versus time. Label the voltage and time axes on your plot, and indicate the value and location of the time constant on your plot.
• Now assume that the switch is initially opened, and that the capacitor is initially uncharged (i.e., v(0) = 0 V). Suppose that the switch is closed at time t=0.
Find the expression for v(t) and make a sketch of the voltage versus time. Label the voltage and time axes on your plot, and indicate the value and location of the time constant on your plot.
• Why is the time constant different for the two cases?
Thank you.