Download EECS 40 Midterm I - Fall 1998 Exam for EECS Students and more Exams Electrical Engineering in PDF only on Docsity!
University of California at Berkeley College of Engineering Dept. of Electrical Engineering and Computer Sciences
EECS 40 Midterm I
Fall 1998 Prof. Roger T. Howe October 1, 1998
_Name: ______________________ Student ID ______________ Last, first
Guidelines
- Closed book and notes; one 8.5” x 11” page (both sides) of your own notes is allowed.
- You may use a calculator.
- Do not unstaple the exam.
- Show all your work and reasoning on the exam in order to receive full or partial credit.
Score
Problem
Points Possible Score
Total 50
- Space Station Power Supply [16 points]
After finishing your B.S. in EECS, you find Silicon Valley too boring and go to work for NASA on the 2010 Space Station project. Your first assignment is to specify the power cable connecting the solar cell panels to one part of the living quarters. The circuit is completed through the frame of the cabin. Note that “ground” is not conveniently located nearby!
100 V
cable
Solar cells
Frame resistance appliances
Is
I 2
(a) [ 4 pts.] We would like to make the cable resistance the same as the frame resistance: R cable = 0.5 Ω. The cable is 10 m in length and is made of aluminum. Given that the resistivity of aluminum is ρ = 2.7 μΩ-cm, what is the diameter of the cable in mm?
(b) [4 pts.] Noting that the cable resistance R cable = 0.5 Ω, what is the current I s in A? Note that there is no need to have solved part (a).
- Two-Terminal Networks [17 points]
2 V -
1 kΩ
1 kΩ
B
0.5 kΩ
A
2 mA
Load
I
V
2 kΩ
(a) [4 pts.] Find the numerical value of the Thevenin resistance RTh between nodes A and B.
(b) [5 pts.] Find the numerical value of the short-circuit current Isc in mA between nodes A andB.
(c) [4 pts.] Find the numerical value of the open-circuit voltage Voc in volts. If you couldn’t solve parts (a) and (b), you can use the following information without loss of credit: I = 3 mA when V = 0.5 V and I = 0.25 mA when V = 1 V. (note that these values are not correct answers for this circuit.)
(d) [4 pts.] Plot the I vs. V relationship for this two-terminal element on the graph below. If you couldn’t solve parts (a), (b), or (c), you can use the default information from part (c) in this part.
I
V
(c) [5 pts.] A voltage source of value 3 V is connected between nodes B and E (with B the positive reference); nodes C, D, and E are connected together. Find the Norton equivalent circuit between nodes A and E, with A the positive reference.
