Physics 2 Lab 6

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Massachusetts Institute of Technology *

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8.02

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Electrical Engineering

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Oct 30, 2023

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Ohm’s Law - Current, Voltage, and Resistance Measurements Lab Number and Title: 215 Ohm’s Law - Current, Voltage, and Resistance Measurements Name: Aaron Hsu Group ID: N/A Date of Experiment: 10/25/22 Date of Submission: 11/1/22 Course and Section Number: PHYS 121A013 Instructor’s Name: Matias Daniel de Almeida Partner’s Names: Paul Svorec, Alex Ack, and Noah Francois 1. Introduction: The goals and objectives of this lab are to learn how to measure current using an ammeter, measure resistance with an ohmmeter, and measure voltage with a voltmeter. Understand the properties of Ohm’s Law and circuits of series, parallel and combination of series and parallel. Understand the characteristics of non-Ohmic device (LED) by measuring the voltage and correspondent current. A resistor is a small carbon conductor that limits the amount of current passing through it which is measured in ohms. The relationship between the current passing through a resistor and the voltage difference is known as Ohm’s Law where and when resistors exhibit constant resistance as 𝑉 = 𝐼 · 𝑅 a function of voltage they are known as ohmic devices. Series circuits involve resistors that are connected so that the same current passes through each resistor and the voltage drop across each resistor is calculated through Ohm’s Law. Parallel circuits include resistors that are connected so that the same voltage is applied to each resistor and the current flowing through each resistor is not the same, but the sum of the current through each resistor is the total current from the power supply. Ohm’s Law is used to calculate the current through each resistor. A light emitting diode or LED for short is a non-ohmic device. 2. Experimental Procedure: The equipment that we used for this lab are a DC power supply, banana cables, LED, electronic connection board, digital multimeter (x2, yellow one for accurate voltage measurement and black one for accurate current measurement), resistors (1 , 2.2 , 𝐾Ω 𝐾Ω 5.6 , 10 , one each), and electronic board connectors. The experimental procedure 𝐾Ω 𝐾Ω

we followed was the same as in the lab manual. First for part one with ohm’s law and measuring current through an electric circuit we setup two digital meters where one was for voltage and the other was for current and setup the setting of the meter along with the connection of the wires are right and then turn on the power supply. We then connected the resistor to the voltage-adjustable port of the power supply and then we would set the voltage across the resistor for 4, 6, 8, and 10 volts as read on the digital voltmeter and observe the current passing through the resistor by the digital ammeter. For the second part with series circuits we would make sure the connection of the wires is right into the power supply, the series circuit, and the digital multimeters. We then would set the voltage to 12 volts and measure the voltage drop across each resistor and then we would measure the current going through the circuit. For the third part with parallel circuits we would make sure the connection of the wires is correct again and set the voltage input across the three resistors that are in parallel to 12 volts. We then measure the current going through each resistor using the digital meter and we have to make sure to turn off the power supply each time we connect the meter and make sure it is set for current measurements. For the fourth part with combined series and parallel circuits we would create a circuit with all of the different resistors and then we would measure the total resistance of this circuit with the ohmmeter after checking and making sure the connection of the wires is correct. For the fifth and final part we would use the 1000 resistor and the LED to create a circuit and make sure the connections are correct and then measure the voltage across the LED and the current through the circuit and we would start with the voltage around 2 volts and increase the voltage to about 3.5 volts by approximately 0.2 - 0.3 volts. 3. Results: Part 1:

Part 2: Part 3: Part 4: Experimental Theoretical Voltage [V] 12 11.92 Resistance [ Ω] 5790 5786.408 Current [mA] 2.07 2.06 Part 5: Potential V b 0 V 1.70 1.81 1.85 1.90 1.96 2.00 2.03 Current I 0 V 0.24 0.47 1.36 3.16 5.81 8.15 8.84

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Part 2 calculations: theoretical voltage across each resistor: Resistor 1: 1000Ω*0.000667A = 6.67 V Resistor 2: 5600Ω * 0.000667A = 3.735V Resistor 3: 2200Ω * 0.000667A = 1.47V Experimental voltage across each resistor: Resistor 1: 6.68V Resistor 2:10.42V - 6.68V = 3.74V Resistor 3: 11.9V - 10.42V = 1.48V Part 3 calculations: + + = R T = 1364Ω 1 10000Ω 1 5600Ω 1 2200Ω 1 1364Ω = 0.00880A 12𝑉 1364Ω 0.00119A + 0.00213A + 0.00539A = 0.00871A 0.00880A ≈ 0.00871A Part 4 calculations: Theoretical ● R T = + + = 5790 Ω ( 1 10000Ω 1 5600Ω ) −1 2200Ω ● V = 12 V ● I = = = 2.07 mA 𝑉 𝑅 12 5790 Experimental ● R T = 5786.408 Ω ● V = 11.92 V ● I = 2.06 mA 4. Analysis and Discussion:

The slope of the voltage compared to the current graph was extremely close to the measured resistance. The number was higher than the color coded value. The value that was calculated for the resistance was exactly the same. The value that was calculated for the current was also exactly the same. The slope value of voltage over current is not constant. This lab was focused on ohm’s law and how to use it in order to determine current, voltage, and resistance throughout different circuits. There was a very small amount of error in this lab due to the precise measurement instruments as well as there being little room to make errors. The results were very accurate. The slight discrepancies between the theoretical and experimental results is most likely because of the resistance in the wires which we assumed to be zero. This is proven very well in the series circuits where the real resistance values were slightly higher than the theoretical values which would be true if there was extra unaccounted for resistance such as the wires. The results that we calculated and measured from this experiment helped us in order to reach the objectives of the lab. 5. Conclusion: How the circuits are designed determines how they will perform and react to current and voltage. Circuits in series and parallel configurations have different currents and behave differently in their own ways. A multimeter that measures volts, amperes, and ohms, a circuit can be analyzed and the resistances, currents, and overall voltages can easily be found at their respective points. Using the experimental tools during this examination, we were able to prove our objectives that came with this task by learning how to measure current using an ammeter, measure resistance with an ohmmeter, and measure voltage with a voltmeter. Understand the properties of Ohm’s Law and circuits of series, parallel and combination of series and parallel. Understand the characteristics of non-Ohmic device (LED) by measuring the voltage and correspondent current. The experiment did not raise too many alarming questions. A change to the experimental design is that we could possibly run more tests in order to get more accurate results.