Download 1.2.2.A Circuit Theory

Activity 1.2.2 Circuit Theory – Hand Calculations
Introduction
Have you ever used a calculator to add some numbers, looked at the answer, and realized
that it was wrong? How did you know that the answer was incorrect? The calculator gave you
an answer; why did you not trust it? You knew the answer was wrong because you
understand the fundamentals of mathematics. Your instinct told you that the answer could not
be correct.
The same is true for circuit analysis. Throughout this course you will be using a Circuit
Design Software to test the circuits that you design. This software will always give an answer,
right or wrong. The only way that you will be able to rely on these answers is if you have an
understanding of the laws of circuit analysis. You must develop the same instinct for circuit
behavior that you have for mathematics.
In this activity you will gain experience applying Ohm’s Law and Kirchhoff’s Voltage and
Current Laws to solve simple series and parallel circuits.
Equipment


Paper & pencil
Calculator
Procedure
1. For each of the resistors shown below, use Ohm’s Law to calculate the unknown
quantity. Be sure to put your answer in proper engineering notation and use the
correct units.
7.45x 10^-3 m/amps
225x 10^-3 Ohms
3080
© 2009 Project Lead The Way, Inc.
DE Activity 1.2.2 Circuit Theory Hand Calculations – Page 1
© 2009 Project Lead The Way, Inc.
DE Activity 1.2.2 Circuit Theory Hand Calculations – Page 2
2. For each of the circuits shown below, calculate the value for RT.
Be sure to put your answer in proper engineering notation and use the correct units.
Calculations:
a)
a)
b)
b)
c)
c)
d)
d)
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DE Activity 1.2.2 Circuit Theory Hand Calculations – Page 3
3. Using the laws of circuit theory, solve for RT, IT, VR1, VR2, & VR3.
Be sure to put your answer in proper engineering notation and use the correct units.
Using the calculations from problem (3), verify your results using Kirchhoff’s Voltage Law.
4. Using the laws of circuit theory, solve for RT, IT, VR1, VR2, VR3, & VR4. Be sure to put
your answer in proper engineering notation and use the correct units.
Using the calculations from problem (4), verify your results using Kirchhoff’s Voltage Law.
© 2009 Project Lead The Way, Inc.
DE Activity 1.2.2 Circuit Theory Hand Calculations – Page 4
5. Using the laws of circuit theory, solve for RT, IT, IR1, IR2, & IR3. Be sure to put your
answer in proper engineering notation and use the correct units.
Using the calculations from problem (5), verify your results using Kirchhoff’s Current Law.
6. Using the laws of circuit theory, solve for RT, IT, IR1, IR2, IR3, & IR4. Be sure to put your
answer in proper engineering notation and use the correct units.
Using the calculations from problem (6), verify your results using Kirchhoff’s Current Law.
© 2009 Project Lead The Way, Inc.
DE Activity 1.2.2 Circuit Theory Hand Calculations – Page 5
Conclusion
1. State two rules for the voltage and current in a series circuit.
2. State two rules for the voltage and current in a parallel circuit.
3. If you remove a single bulb from an inexpensive string of Christmas tree lights, all of the
lights in the entire string will go off. Are the bulbs connected in series or parallel?
Explain.
Going Further – Optional
The circuit shown below is a series/parallel circuit. That is, some of its resistors are connected
in series and some are in parallel. Using the laws of circuit theory, solve for R T & IT.
© 2009 Project Lead The Way, Inc.
DE Activity 1.2.2 Circuit Theory Hand Calculations – Page 6