ECE 252 Introduction to Electrical Engineering
Lesson 1. Basic Elements and Circuit Laws Homework
Version S16
Homework partner name: _______________________Homework partner name: ________________________
Important: Sketch each circuit. Label all circuits with appropriate currents and voltages.
1. Homework policy: Copying homework and all other forms of academic dishonesty are forbidden. Use of
homework assignments from previous terms is forbidden, as is looking up solutions on line, looking at the papers
of others, showing others your papers, and comparing answers. Getting aid from other students on homework is
acceptable if limited to general solution concepts and methods. The team members must work together, face-toface, on all parts of the assignment, that is, dividing up the work is not permitted. To verify that you have worked
together, each team member must sign each problem solution at the time the problem is solved. If it is impossible
for the team members to work together, each individual should turn in a separate homework assignment.
Please carefully read the above policy, and then comment below. You will be given credit so long as your
comments are thoughtful and sincere.
Signatures: ________________________________________________________________________
2. Quickies
a) A +3 coulomb charge is moved from point A, which has a voltage of 15 V with respect to ground, to point B,
which has a voltage of 25 V with respect to ground. The work done on the charge is _________ J. The answer is
an integer.
b) 480 coulombs of charge flows through a wire at a constant rate over a period of 4 minutes. The current in the
wire is _______________ A. The answer is an integer.
c) A 120 V toaster carries a current of 15 A when it toasts a slice of bread for 3 minutes. The power consumed
by the toaster is _________ W. The resistance of the coils in the toaster is _______ Ω. The energy consumed by
the toaster is ___________ J or ________ kWh.
d) For an ideal independent _____________________ source, the voltage is independent of the current. It can
deliver any current (from 0 to infinity) in either direction.
e) For an ideal independent _____________________ source, the current is independent of the voltage. It can
have any voltage (from 0 to infinity) with either polarity.
Signatures: ________________________________________________________________________
3. E = 20 V, R1 = 800 Ω, R2 = 1200 Ω. Do not solve by combining resistors in series. a) Define and label a
current for the circuit. Define and label a voltage across each resistor. b) Write Kirchhoff’s Voltage Law (KVL)
for the circuit. c) Write an Ohm’s Law equation for each resistor. d) Solve these three equations to find the current
in the circuit. Give your answer in mA. The answer is an integer.
Signatures: ________________________________________________________________________
4. E = 9 V, R1 = 60 Ω, R2 = 180 Ω. Do not solve by combining resistors in parallel. a) Define and label currents
in R1 and R2. Define and label voltages across R1 and R2. b) Write a Kirchhoff’s Current Law (KCL) equation at
one of the essential nodes. c) Write a KVL equation for the left mesh. Write a KVL equation for the right mesh. d)
Write an Ohm’s Law equation for each resistor. e) Solve these 5 equations to find I. Give your answer in mA. The
answer is an integer.
Signatures: ________________________________________________________________________
5. E = 240 V, R1 = 16 Ω, R2 = 36 Ω, R3 = 72 Ω. Do not combine resistors in series and parallel. a) Define and
label a current in each resistor and a voltage across each resistor. b) Write a Kirchhoff’s Current Law (KCL)
equation at one of the essential nodes. c) Write a KVL equation for the left mesh. Write a KVL equation for the
right mesh. d) Write an Ohm’s Law equation for each resistor. e) Solve these 6 equations to find the current in
each resistor. The answers are integers.
Signatures: ________________________________________________________________________
6. C1 = 15 A, C2 = 4 A, E1 = 20 V, E2 = 30 V, R1 = 40 Ω, R2 = 50 Ω. Find I2. The answer is an integer.
Signatures: ________________________________________________________________________
7. E1 = 25 V, E2 = 72 V, R1 = 27 Ω, R2 = 100 Ω, I1 = 4.5 A. Find V1. The answer is an integer.
Signatures: ________________________________________________________________________
8. E1 = 9 V, E2 = 10 V, R1 = 5 Ω, R2 = 11 Ω, R3 = 8 Ω, I1 = 1 A, Ix = 3 A, Iy = 6 A. Find the voltage at point A
with respect to ground. The answer is an integer.
Signatures: ________________________________________________________________________
BONUS (no partial credit). It is wise to become adept at solving simultaneous equations using modern tools.
Advanced calculators have this capability, as do computer algebra systems, such as Maple. Use either a calculator
with equation-solving capability or a computer algebra program to find V1, V2, V3, and V4 in the following
simultaneous KVL equations. The answers will not be integers.
5V1 – 3V2 + 8V3 + 9V4 + 17 = 0
10V1 – 12V3 – 4V4 – 6 = 0
-2V2 + 7V3 – 14V4 – 16 = 0
17V1 + 18V2 – V3 – 13V4 = 0
Describe the tools you use and how to use them to solve this problem. Give your answers in decimal form.
Signatures: ________________________________________________________________________