PHY 172 Lab Report 2

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St. Augustine's University *

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172

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Electrical Engineering

Date

Dec 6, 2023

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doc

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Uploaded by MagistrateSeaLionMaster941

Justin Alvarado Resistance in a Wire Remote Lab This lab is designed for a student working remotely after completing Ohm’s Law Remote la b . This lab uses the Resistance in a Wire and Circuit Construction Kit DC simulation from PhET Interactive Simulations at University of Colorado Boulder, under the CC-BY 4.0 license. https://phet.colorado.edu/sims/html/resistance - in - a - wire/latest/resistance - in - a - wire_en.html https://phet.colorado.edu/sims/html/circuit - construction - kit - dc/latest/circuit - construction - kit - dc_en.html Learning Goals: 1. Explore the characteristics of a resistor that are variable in this model. 2. Identify how each characteristic affects the resistance and current flow. 3. Explain your ideas about why the characteristics change the resistance and current flow. 4. Use understanding to make predictions about a circuit with lights and batteries. Develop your understanding: 1. Open Resistance in a Wire , then explore to develop your own ideas about how the construction of a resistor affects its resistance and also ability to allow current to flow. Describe several of your experiments and your observation with captured images from the simulation. Table 1: (Constants: Area – 7.50 cm 2 , Length – 10 cm) Resistivity (  cm) Length (cm) Area (cm 2 ) Resistance (ohms) .10 10 7.50 .133 .25 10 7.50 .333 .50 10 7.50 .667 .75 10 7.50 1.00 1.00 10 7.50 1.33

4/2/20 Loeblein https://phet.colorado.edu/en/contributions/update - success/5435 page 1 Table 2: (Constants: Resistivity - .50  cm , Length – 10 cm) Resistivity (  cm) Length (cm) Area (cm 2 ) Resistance (ohms) .50 10 2.53 1.98 .50 10 5.05 .990 .50 10 7.62 .656 .50 10 10.13 .494 .50 10 12.34 .405 Table 3: (Constants: Resistivity - .50  cm , Area , 7.50 cm 2 ) Resistivity (  cm) Length (cm) Area (cm 2 ) Resistance (ohms)

.50 2.51 7.50 .167 .50 5.69 7.50 .379 .50 10.01 7.50 .667 .50 15.06 7.50 1.00 .50 20.00 7.50 1.33 In Experiment 1, I thought of making both the area and length of the resistor a constant value of 10 cm in length and 7.50 cm 2 in area. From the experiment data I collected, I came to the conclusion that as you increase the resistivity of a resistor with constant length and area, the resistance would increase as well. This would then therefore decrease the current flow as the resistance increases. In Experiment 2, I then chose to make length and resistivity constant at 10 cm and 50  cm. From this experiment I found that as I increased the area of the resistor, the resistance would decrease. This makes sense because by increasing the surface area, the current has a wider enclosure to flow through. Lastly in Experiment 3, I made the resistivity of 50  cm constant as well as the area of 7.50 cm 2 . From this experiment, as we increased the length of the resistor, the resistance in ohms increased as well, therefore making a current more difficult to flow through. Demonstrate your understanding: Directions: As you answer the questions, explain in your own words why your answer makes sense and provide evidence from your #1 experiments. Add more experiments to #1 if you need to get better evidence. 2. If you change the cross sectional area of the resistor, how does a. the resistance change? (answer, explain, evidence) Both resistance and area are inversely proportional to each other based on the equation where R is the resistance, is the resistivity of the resistor, L is the length and A is the cross sectional area. So, by increasing the area of a resistor, the resistance would decrease and by decreasing the area, the resistance of the resistor would increase proportionally. Evidence of this can be found in my second experiment under Table 2.

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b. the current through a circuit change? (answer, explain, evidence) Ohm’s law states that current is directly proportional to the voltage supplied and inversely proportional to the resistance. So therefore, assuming the voltage is constant, as the surface area of a resistor increases, the current would also increase because there is more room for the current to flow. Also, if the surface area of a resistor decreases, the current would decrease based on the same reasoning. Evidence for this can also be found in Table 2 of Experiment 2. 3. If you change the length of the resistor, how does a. the resistance change? (answer, explain, evidence) By changing the length of a resistor, its resistance is directly proportional to its length. So by increasing the length of a resistor, the resistance will also increase as well and the opposite is also true. Evidence for this can be found in Table 3 of Experiment 3. b. the current through a circuit change? (answer, explain, evidence) Referring back to Ohm’s law, current is directly proportional to the voltage supplied and inversely proportional to the resistance. So as the length of a resistor increases, since the resistance increases, the current flow through the resistor will decrease. As the length of a resistor decreases, the current flow would increase since the total resistance in ohms would be low. Evidence for this can be found in Table 3 of Experiment 3. 4. If you change the resistivity of the resistor, is the effect like changing the length or changing the area? (answer, explain, evidence) By changing the resistivity of the resistor, the effect is like changing the length of the resistor. Resistivity and resistance are directly proportional so as the resistivity increases, the resistance will increase and. the opposite is true as well. Evidence for this can be found in Tables 1 and 3 of Experiments 1 and 3. 5. During manufacturing, how is the resistivity of a resistor changed? Cite your references In manufacturing, resistivity of a resistor can be altered by adding another material in the sheet used to make a resistor. Also, patterns can be cut in the sheet that allow current to either increase or decrease based on the needs of the product being manufactured. Electrical resistivity: RESISTOR FUNDAMENTALS: Resistor Guide . EEPower. (n.d.). https://eepower.com/resistor-guide/resistor-fundamentals/electrical-resistivity/#:~:text=Often %20resistor%20manufacturers%20increase%20resistance,a%20pattern%20in%20the%20sheet . rightone is 6. Consider the two circuits below in which the left resistor is

Use your understanding of voltage, resistance, and current to answer these questions: a. What do you think will happen when the switches are turned closed? (answer, explain, evidence) When the switches are turned closed, the current is fully connected and therefore, voltage from the battery will power a current that runs through the wires and into the lightbulb. The lightbulb will then power on. The right circuit, which resistor is 30 ohms, will have not as much current flowing through it as the left one because the left one has less resistance. More resistance means that less current will flow through the circuit. I have attached a picture as evidence. b. How do you think the lights’ brightness will compare? Based on the picture above, in the circuit with the 10 ohms resistor the light will be brighter than the circuit with the 30 ohms resistor because there is more current flowing into the lightbulb. With more current, you will get a brighter lightbulb and with less current flow, you will get a dim light bulb. This is how light switches work with built in light dimmers work. c. Open the Intro s creen of Circuit Construction Kit DC. Build the 2 circuits and check your answers. Insert a capture of the circuits with the switch closed for supporting evidence.