Lab 04_Resistors

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Apr 3, 2024

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BIOMEDE 3702 LAB PROCEDURE: Resistors Learning Outcomes: Students will be able to…  Identify different resistor values.  Assemble a simple resistor circuit with components in series and parallel.  Learn the basic operation of an oscilloscope and a function generator. Materials: 1. Solderless breadboard 2. Multimeter 3. Wire box 4. Ammeter 5. Resistors – 3x 100 Ω 6. Arduino (for power supply) 7. Oscilloscope a. One gray lead BNC hook probes 8. Function generator a. One black lead BNC connector with red/black alligator clips. Setting up your Power Supply: To get a 5 V output you will be using the Arduino. Please follow these steps: 1. Plug the Arduino into the USB isolator using the USB A/B connector. 2. Plug the USB isolator to the computer using the USB micro connector. 3. Use two wires to connect the Arduino 5V and the GND to the breadboard. Resistors Circuit Experiment #1: Understanding current, voltage and resistance Figure 1: First Circuit 1. Select from the resistor pile three 100 Ω. Review “ How to Read Resistor Values” Select from the resistor pile three 100 Ω. Review “How to read a resistor values” . 2. Connect the ammeter and a one 100 Ω resistor in series, as shown in the schematic above.

BIOMEDE 3702 Note : Putting two electrical elements in series means that the current flowing through each component is the same. Think back to your prelab and the class. 3. Record the current passing through your ammeter. 4. Now measure the voltage across the resistor with your multimeter. 5. Measure the voltage across the ammeter with your multimeter. Record these numbers in your post lab at the end of this document. 6. Two students argue and disagree about this first circuit: Student A says, “The resistor is absorbing current.” and Student B says, “The resistor does not absorb current.” a. With which student do you agree, and why? Discuss with your lab-mate. b. How could you experimentally test which student is correct? Draw a schematic of your test circuit. Write a description of what you expect to measure if Student A is correct, and what you expect to measure if Student B is correct. Record in Post lab c. Perform your experiment and record your results and conclusions. Explain to a TA before proceeding!

BIOMEDE 3702 Resistors Circuit Experiment #2: Series circuit Figure 2: Second Circuit 1. Add an additional 100Ω in series with the 100Ω resistor in your original circuit (see schematic above). Note: Refer to the “How to use a breadboard document" and the prelab to connect this. 2. Measure and record the current in your circuit: Record in your Post lab a. Is the current the same that you found in the pre-lab? b. How did current change when you added the second resistor in series? c. What does this tell you about the resistance of two resistors in series? 3. Measure and record the voltage in your circuit: Record in your Post lab  Across the entire circuit ( across the red +5V input to the black ground banana plugs )  Across each resistor  Across the ammeter. a. What is the voltage across the ammeter? What does this tell you about the resistance of the ammeter? b. Add the voltages you measured across each resistor and the ammeter and compare that sum to the voltage you measured across the entire circuit. c. Kirchoff’s law says that the sum of the voltages across all devices in a loop is zero. Is your experiment consistent with Kirchoff’s voltage law? 4. In many circuits, two resistors in series are often called a voltage divider . Draw a diagram that incorporates the results of your measurements and explain why this type of resistor arrangement has this name.

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BIOMEDE 3702 Resistors Circuit Experiment #3: Parallel circuit Figure 3: Third Circuit 1. Add to your existing circuit a third 100Ω resistor that is in parallel to R 2 . Note : Putting two electrical elements in parallel means that the voltage across both parallel elements is the same. 2. Measure and record the current passing through your ammeter: a. How has the current changed with the addition of a parallel resistor? b. What does this tell you about the resistance of the circuit as a whole? c. Divide the current you measured through this 3-resistor circuit by the current you measured through your 2-resistor circuit (Experiment 2, step 2), and record. d. Why is the current through the 3-resistor circuit larger than the current through the 2- resistor circuit? 3. Measure and record the voltage across each of the three resistors and record. a. Approximately what fraction of the total input voltage (5V) is “dropped” across the two resistors in parallel? b. What is the voltage drop across each of the parallel resistors? Compare the two values. Now, recall the voltage drop across each of the resistors in the 2-resistor series circuit in Experiment 2, and compare those two values. What is different about the two values in the parallel circuit versus the two values in the series circuit? 4. Move the ammeter in your circuit such that you are measuring the current through each of the parallel resistors. a. Record the current measured through each resistor. b. Kirchoff’s current law says that the sum of the currents into a node is zero. Is your experiment consistent with Kirchoff’s current law? 5. Two resistors in parallel is called a current divider. Draw a diagram that incorporates the results of your measurements and explain why this type of resistor arrangement has this name.

BIOMEDE 3702 WARNING! Make sure you have all the data and/or images required for your Post-Labs. Not doing so could lead you to re-doing the experiment. Oscilloscope and Function Generator Tutorial As part of this lab you are required to run through the Oscilloscope and Function Generator Tutorial . These tutorials are found in Carmen. Before you leave have the TA check your work for these tutorials. Run the Oscilloscope tutorial first. THE POINT In this lab, we were able to create simple resistor circuits that allowed us to understand the relationship between voltage, current and resistance. We saw how current behaves under different resistor arrangements, as well as voltage. Particularly, we saw two arrangements (voltage divider and current divider) that allow us to control the amount of voltage or current split resulting from a resistor setup. We also began working with the oscilloscope and function generator as tool to create and observe signals. Learning Outcomes: Students will be able to…  Identify different resistor values.  Assemble a simple resistor circuit with components in series and parallel.  Learn the basic operation of an oscilloscope and a function generator.

BIOMEDE 3702 POST LAB: Resistors Table 1 : Summary of Experimental Data for Resistors Experiments (3 points) Experiment #1 Experiment #2 Experiment #3 Current (mA) Voltage across (V) R 1 R 2 R 3 Ammeter Circuit Voltage Sum (V) Measured Arduino Output (V) Circuits Experiment #1 1. Two students argue and disagree about this first circuit:  Student A says, “The resistor is absorbing current.”  Student B says, “The resistor does not absorb current.” a. How did you experimentally test which student was correct? Show a labeled schematic of your circuit, including experimental result measurements. (2 points) b. Which student was correct? Discuss your results with your performed experiment. (1 points) Circuits Experiment #2 1. Show detailed schematic of your circuit that incorporates the results of experiment #2 (series circuit), including all voltage, current and resistance values measured in this experiment. (2 points)

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BIOMEDE 3702 2. Discuss how current is affected by adding a second resistor in series to the circuit. Relate that change to the resistance of your circuit. (2 point) 3. Explain why this resistor arrangement is called a voltage divider. (1 point) 4. What is Kirchoff’s voltage law? Is your experiment consistent with that law? Explain. (2 point) Circuits Experiment #3 1. Show detailed schematic of your circuit that incorporates the results of experiment #3 (parallel circuit), including all voltage, current and resistance values measured in the experiment. (2 points) 2. Discuss how current is affected by adding a third resistor in parallel in the circuit. Relate that change to the resistance of your circuit. (2 points) 3. Explain why this resistor arrangement is called a current divider. (1 point) 4. What is Kirchoff’s current law? Is your experiment consistent with that law? Explain. (2 point)

BIOMEDE 3702 Challenge Question 4: Note: Challenge questions in post-labs are bonus and optional. These questions are designed to be challenging. Please submit your attempts here on Carmen. 1. What is the function of a Wheatstone Bridge Circuit? Write the step-by-step derivation of it and build one in Tinkercad.