ELEC 101, Spring 2005
Prof. Rich Kozick

Homework 4

Date Assigned: Friday, February 4, 2005
Date Due: Monday, February 14, 2005 (for items 3 and 4 below)

  1. Schedule for the week of February 7:

  2. Reading: Please continue to study Chapter 2 in the Bobrow text, Sections 2.1 and 2.2 on nodal analysis. For the week of February 14, we will discuss Section 2.4 on operational amplifiers (op amps).

  3. Bridge circuit: Recall the bridge circuit that we used in Lab 3 to detect a difference in temperature. Let us consider how we can calibrate the bridge to account for non-identical thermistors.


    Suppose the thermistors RT1 and RT2 are not identical. At room temperature, RT1 = 5000 ohms and RT2 = 6000 ohms. At a higher temperature, RT1 = 3000 ohms and RT2 = 4000 ohms. Suppose that RA = sqrt(5000*3000) = 3870 ohms, but that RB is a potentiometer whose resistance can be varied from 100 ohms to 10,000 ohms.

    (a) What value should RB have in order to "balance the bridge", i.e., set vout = 0 V, at room temperature? Please explain.

    (b) If vout is a positive voltage, which thermistor is warmer? Please explain.

  4. Nodal analysis: Please do problems 2.6, 2.7, 2.8, and 2.10 in the Bobrow text.
Thank you.