9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
PLTW ENGINEERING
Activity 1.1.5a
Circuit Theory: Hand Calculations
Distance Learning Support
Check with your teacher about:
What work you need to turn in and how to submit it
Collaboration strategies
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 you may have entered a number incorrectly, because the answer could
not be correct.
The same is true for circuit analysis. Throughout this course you will be using
Circuit Design Software (CDS) to test the circuits that you design. This software will
always give an answer, whether it's 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.
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
1/7
9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
EQUIPMENT
Calculator
RESOURCES
Circuit Theory Laws presentation
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
2/7
9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
Procedure
Presentation: Review Circuit Theory Laws.
For each of the resistors shown, use Ohm’s Law to calculate the unknown
1
quantity and express your answer in proper engineering notation and correct
units.
I = 7.45 mA
30.8 V
7.45 * 10^-3 A
R=
225.81 kΩ
225.8 * 10^3 Ω
30.8 * 10^1 V
300 V
R = 240 Ω
I = 2.94 mA
240 * 10^1 Ω
2.94 * 10^-3 A
300 * 10^1 V
Figure 1. Update Description Using Caps
2
For each of the circuits shown below, calculate the value for RT using proper
engineering notation and correct units.
a. Series circuit
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
3/7
9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
Rt = 10.87 kΩ
Figure 2. Series Circuit
b. Parallel circuit
Rt = 565 Ω
Figure 3. Parallel Circuit
c. Parallel circuit
Rt = 67 Ω
Figure 4. Parallel Circuit
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
4/7
9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
3
Using the laws of circuit theory, solve for RT, IT, VR1, VR2, and VR3.
Be sure to put your answer in proper engineering notation and use the correct
units. Using your calculations, verify your results using Kirchhoff’s Voltage Law.
Vr1 = V
Vr2 = V
Vr3 = V
Rt = 1940 Ω
It = 4.64 kA
Figure 5. Series Circuit
4
Using the laws of circuit theory, solve for RT, IT, VR1, VR2, VR3, and VR4. Be sure
to put your answer in proper engineering notation and use the correct
units. Using your calculations, verify your results using Kirchhoff’s Voltage Law.
Vr1 = 669.6 mV
Vr2 = 2.48 V
Vr3 = 818.4 mV
Vr4 = 2.03 V
Rt = 24.2 kΩ
It = 248 µA
Figure 6. Series Circuit
5
Using the laws of circuit theory, solve for RT, IT, IR1, IR2, and IR3. Put your
answer in proper engineering notation and use the correct units. Using your
calculations, verify your results using Kirchhoff’s Current Law.
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
5/7
9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
Ir1 = 1.46 mA
Ir2 = 1.76 mA
Ir3 = 2.55 mA
It = 5.77 mA
Rt = 2.075 kΩ
Figure 6. Parallel Circuit
6
Using the laws of circuit theory, solve for RT, IT, IR1, IR2, IR3, and IR4. Put your
answer in proper engineering notation and use the correct units. Using your
calculations, verify your results using Kirchhoff’s Current Law.
Ir1 = 2.222 mA
Ir2 = 0.6 mA
Ir3 = 1.818 mA
Ir4 = 732 uA
It = 5.372 mA
Rt = 1.117 kΩ
Figure 7. Parallel Circuit
7
The circuit shown below has a compound circuit which contains a series and
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 RT and IT.
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
6/7
9/23/21, 11:17 AM
Activity 1.1.5.a: Circuit Theory: Hand Calculations
It = 216.61 mA
Rt = 908.26 Ω
Figure 8. Compound Circuit
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 go off. Are the bulbs connected in
series or parallel? Explain.
Proceed
to next
activityis the same throughout
1. Add up the ohmic values.
The
current
the circuit
2. Ohm's law: I = V/R; Reciprocal formula: (R1^-1 + R2^-1 + R3^-1
+ Rn^-1)^-1 = Rt
3. They are connected in series. This is because all of the other
lights go off when one point of the circuit fails, which is a key
characteristic in a series circuit. In a series circuit, the electrons
only have one possible path to traverse down.
https://pltw.read.inkling.com/a/b/495d2ced70ec40e9b5d51a1fe6a96b07/p/e984dc29628d4c54b2c9bb9997ca4dfa#f3ca2f7392b84e12970ebdf44c984972
7/7