Download EE 261 Midterm Exam 3 - Electrical Circuits - Prof. Aziz S. Inan and more Exams Microelectronic Circuits in PDF only on Docsity!
University of P J rtland
Sch JJ l of Engineering
EE 261-Electrical Circuits-3 cr. hrs.
Fall 2002
Midterm Exam # 3
(Friday, November 22, 2002)
(Closed Book Exam, Three Formula Sheets Allowed)
(Total Time: 55 minutes)
Name:_______________________ J
Signature:__________________ _ J
“ An honest mind possesses a kingdom. ”
Lucius Annaeus Seneca (4B.C.−65A.D.)
“ Honest people are the true winners of the universe. ”
Anonymous
Who am I? Here is a hint. You have been using
my two laws constantly in electrical circuits.
Who is my colleague? I will give you three hints:
1. He invented the Bunsen burner.
2. Together, we discovered spectroscopy.
3. We also discovered cesium & rubidium.
Oops?
NOTE: On all the problems, please show all your work, and provide
the appropriate units for your answers. Also mark on the schematic to
show any currents or voltages that you define in your solution.
- (30 points) For the circuit shown below, find the mathematical expression
for the current i L
(t) for t > 0. (Answer: ( ) 5 15 ,(mA)validfor 0
8
- 410
= − + ≥
− ×
i t e t
t
L
.)
10 u (− t ) (mA) (^) 1 0 u ( t ) (V) R
1
=3 k Ω i L
( t )
R
2
=2 k Ω
L =5 μ H
- (Total: 40 points) Consider the circuit shown below.
v ( t )
R
3
R
2
L =4 m H
R
1
C =25 n F
3 u ( t ) (V)
(a) (15 points) Find the roots of the characteristic equation of this circuit and
determine the type of the response. (Answer: Equal roots given by
5
1 2
s , s =− 10 ‡Critically-damped response.)
(b) (10 points) Based on what you found in part (a), write the general form
of the forced response. (Answer: ( ) (^ )^ ,validfor 0 3
10
1 2
5
−
v t A Ate A t
t
.)
(c) (15 points) Solve the unknown coefficients in the v ( t ) expression. Show
all your work. (Answer: 2 V, 2 10 V, 2 V 3
5
1 2
A = − A =− × A = .)
