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ECE 252 Introduction to Electrical Engineering
Lesson 3. Circuit Solving with Kirchhoff's Laws Homework
Version S17
Homework partner name: _______________________Homework partner name: ________________________
1. Completely label the diagram. Use Ohm's Law and Kirchhoff's Laws to write enough equations to solve for the
current through and the voltage across each element. Do not solve. Note: The purpose of this exercise is to give
you practice in carefully labeling circuits and writing the circuit equations. Caution: There is a dependent source
in this problem; you must decide if it is a voltage source or a current source. Another caution: Make sure your
current directions match your voltage polarities for resistors.
Kirchhoff’s Voltage Law:
Kirchhoff’s Current Law:
Ohm’s Law:
Signatures: ________________________________________________________________________
2. The circuit below is labeled with appropriate voltages and currents.
The equations for the circuit below are as follows:
Kirchhoff’s Voltage Law:
α: -12 + V3 – V5 – 6 + V8 = 0
β: -V8 – V4 + V7 = 0
γ: V4 + 6 + V9 = 0
Ohm’s Law:
V5 = 3×5
V9 = 9I9
V7 = 7I7
V8 = 8I8
V4 = 4I4
Kirchhoff’s Current Law:
A: -3 – I8 – I7 = 0
C: I8 – I6 – I4 = 0
D: I7 + I4 – I9 = 0
Cross out the equations that are not needed to solve for V9. Do not solve. Note: The purpose of this exercise is to
help you recognize the features of a circuit that are not necessary for a solution. Hint: If an unknown appears in
but one equation, and that unknown is not needed, the equation (and unknown) can be eliminated.
Signatures: ________________________________________________________________________
3. E = 5I, R1 = 4 Ω, R2 = 2 Ω, Is = 2 A. Find I. The answer is an integer. Caution: There is a dependent source in
this problem. Carefully consider whether it is a voltage source or a current source.
Signatures: ________________________________________________________________________
BONUS (no partial credit) Knowing the names for the powers of 10 can be valuable. Fill in the table below. Some
of the values are filled in for you.
Factor
1021
1018
1015
1012
109
106
103
Name
giga
Symbol --------------------------------------E
-------------------------------------------------------------------------------------------------------------------
Factor Name
10-2
10-3
10-6
10-9
10-12
10-15
10-18
atto
Signatures: ________________________________________________________________________
Symbol
m