Copy of Lab 3 - Kirchhoff Circuit Rules

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University of Massachusetts, Amherst *

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152

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Electrical Engineering

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Jan 9, 2024

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pdf

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Uploaded by ConstableMoon12743

Lab 3 - Kirchhoff’s Circuit Rules Overview In Labs 2 you studied Ohm’s Law and learned how different combinations of resistors in series or parallel resulted in an equivalent resistor. It turns out there are rules that define how these equivalent resistances work. They are Kirchhoff’s Circuit Rules . There are two rules. The first rule is the junction rule. The sum of the currents flowing into a junction is equal to the sum of the current flowing out of a junction. (1) The foundation for this rule is that electric charge is conserved. The second rule is the loop rule. The sum of the voltages around a loop is zero. (2) The foundation for the loop rule is that energy is conserved. In this lab you are going to construct circuits to test these rules. Part 1 - Kirchhoff’s Loop Rule Construct a circuit with a 10k (brown, black, orange, gold) and two 4.7k (yellow, purple, red, gold) resistors in series . The three resistors along with the 3.3V supplied by the iOlab make a loop circuit. Your circuit should look like this:

● Red alligator clip is connected to 3.3V. ● Blue alligator clip is connected to A7. ● Yellow alligator clip is connected to A8. ● White alligator clip is connected to GND. The blue and yellow alligator clips are intentionally not connected to the circuit because you will move the clips to three positions around the circuit loop and measure the voltage. Think back to Lab 2 - Ohm’s Law when you constructed a circuit with resistors in series. The two resistors in series had an equivalent resistance of equal to the sum of the individual resistor: 1. If two or more resistors are in series, what must be true about the current through each resistor? Explain your answer. The current is the same in each resistor because the current coming out of the first resistor flows into the second resistor thus they must have the same output. 2. Using Ohm’s Law and Kirchhoff’s Loop Rule, derive the equation for the equivalent resistance for resistors in series. Show your work. V total = I1R1 + I2R2 Loop Rule: Sum of I = 0 -> I1 = I2

I total R total = I total (R1+R2) R total = R1+R2 Setup the iOLab and application: ● Launch the iOlab application on your computer. ● Make sure the dongle is connected to the USB port of your computer and the iOLab is turned on. ● Check the A7 and A8 sensors. Now it’s time to take some data: ● Across the first resistor, connect the blue clip to the red clip position and connect the yellow clip to position 1. ● Click and record for about 5 seconds then stop. ● Across the second resistor, connect the blue clip to position 1 and move the yellow clip to position 2. ● Click continue and record data for 5 seconds then stop. ● Across the third resistor, connect the blue clip to position 2 and the yellow clip to position 3. ● Click continue and record data for 5 seconds then stop. When you are done your data should look something like this: 3. Take a screenshot of your iOLab application with the data and paste here:

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