Lab Week 6. Quiz #3 Voltage Divider Homework P11, P12 Kirchhoff's Voltage Law (KVL) Kirchhoff's Current Law (KCL) KCL + KVL Module Report tips

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1 Lab Week 6 Quiz #3 Voltage Divider Homework P11, P12 Kirchhoff's Voltage Law (KVL) Kirchhoff's Current Law (KCL) KCL + KVL Module Report tips

2 Quiz 3 Voltage Divider (20 pts.) Please clear desks and turn off phones and put them in back packs You need a pencil, straight edge and calculator 10 minutes Keep eyes on your own paper Follow the same format as for homework

3 Homework - P11 (a) Determine the circuit current for the simplified circuit in P9 if R1 R4 are equal to 100Ω and Vin is equal to 9 V, (b) Use Ohm s Law to confirm the voltage drop at VA, and (c) Use the expression for P9 part (b) to determine VA using the voltage divider method. Show every step, units, and unit conversions for full credit.

4 Homework - P12 (a) Determine the voltages at nodes A, B, C and D. (b) Determine the currents I1 I7. (c) Determine the power generated or consumed by each component, and (d) Determine if conservation of power exists in this circuit. Label each step and include units and unit conversions for full credit.

Kirchhoff's Laws Introduced by the German physicist Gustav Robert Kirchhoff in 1847, 21 years after Georg Simon Ohm developed his famous law (Ohm s Law!).

5 Kirchhoff's Laws Introduced by the German physicist Gustav Robert Kirchhoff in 1847, 21 years after Georg Simon Ohm developed his famous law (Ohm s Law!). Kirchhoff's Laws state that conservation of charge and conservation of energy will always be true in an electric circuit. The laws discovered by Kirchhoff represent the foundation of electric circuit analysis. Many equations used in electrical engineering are derived from these two laws!!

6 Kirchhoff s Current Law (KCL) KCL represents conservation of charge mathematically by the following equation: N n=1 i n = 0 (KCL) KCL states that the sum of all currents entering or leaving a node equals zero Amps (0 A)

7 Kirchhoff s Current Law (KCL) convention Currents entering a node are positive (+) Currents leaving a node are negative (-) This is just a convention! Look at the image and convince yourself why this makes sense. 3 Amps go in to Node A, so 3 Amps must go out! Node A 3 Amps 1 Amp 2 Amps = 0

8 Kirchhoff s Current Law (KCL) Exercise Find the current I o using KCL Source: Alexander, C. K., & Sadiku, M. N. (2007). Fundamentals of electric circuits. New York, NY: McGraw-Hill Higher Education.

9 Kirchhoff s Voltage Law (KVL) KVL represents conservation of energy mathematically by the following equation: N n=1 v n = 0 (KVL) KVL states that the sum of all voltages around a closed loop is equal to zero Volts (0 V)

Voltage rise and voltage drops depend on the KVL Loop Look at the image and convince

10 Kirchhoff s Voltage Law (KVL) convention Voltage drop is positive (+) Voltage rise is negative (-) KVL loop goes clockwise These are just a conventions! Voltage rise and voltage drops depend on the KVL Loop Look at the image and convince yourself why this makes sense. 12 Volts are supplied, 12 Volts are consumed! 12 Volts + 2 Volts + 4 Volts + 6 Volts = 0

11 Kirchhoff s Voltage Law (KVL) Exercise Find voltage V using KVL Source: Alexander, C. K., & Sadiku, M. N. (2007). Fundamentals of electric circuits. New York, NY: McGraw-Hill Higher Education.

12 KCL + KVL Kirchhoff s laws can be used together to analyze complex circuits KCL is applied at nodes I 1 I 2 I 3 KVL is applied around loops Lets solve the circuit on the right using KCL and KVL

13 KCL + KVL Exercise Use KCL and KVL to find I 1, I 2 and I 3 I 1 I 2 I 3

14 Module Report A module report is due after every lab module Module 1 report is due next week at the beginning of your lab NO LATE MODULES ARE ACCEPTED!

15 DO s and DON Ts for good Module Reports DO NOT WAIT MORE THAN 1 WEEK to talk to your TA leader or instructor if you are not getting good report grades DO NOT WAIT until the last minute to work on your lab report DO NOT plagiarize ANYONE S work. If you do, we will take action following UTEP s policies. DO read the module before showing up to the lab DO take notes while doing the lab DO ask for help from your TAs. We have 3 TAs per lab DO communicate with your teammates

16 Writing a good report Always explain figures and tables. Explain what methods you used to analyze a circuit (where applicable). Did you use Ohm s Law, KCL, KVL? Explain your results. Why do you think you got those particular results from your circuit? Does the circuit obey Ohm s Law, KCL, KVL? Take good measurements and data. Always be aware that your measurements should be close to your theorical results. If they are not, try to explain why.

17 Exercise: Writing a good report What can you tell me about the figure below?

18 What s Next in Week 7? Will introduce LAB Module II Strain Gauge (Voltage Divider) LECTURE Quiz #4 Equivalent Circuits Op-Amp KCL Please bring laptops to all lectures and labs.

19 Questions?

Sirindhorn International Institute of Technology Thammasat University at Rangsit

Sirindhorn International Institute of Technology Thammasat University at Rangsit School of Information, Computer and Communication Technology COURSE : ECS 304 Basic Electrical Engineering Lab INSTRUCTOR