Resistance in a Wire

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Ivy Tech Community College, Indianapolis *

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102

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Electrical Engineering

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Dec 6, 2023

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docx

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Resistance in a Wire Lab 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. The resistance of the wire is directly proportional to the length and inversely proportional to the cross-sectional area. The p is the resistivity, which is the characteristic of the material. As I increase the resistivity, the resistance also increases and there are more dots on the wire. When I increase the length, the wire increases in size and so does the resistance. When I increase the area, the resistance decreases dramatically. 4/2/20 Loeblein https://phet.colorado.edu/en/contributions/update-success/5435 page 1
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) Evidence is shown above. When I increased the cross-sectional area of the resistor, the wire increases in size but the resistor decreases. The resistance is inversely proportional to the cross-sectional area. b. the current through a circuit change? (answer, explain, evidence) When the resistance is decreased, the cross-sectional area increases and so does the current. 3. If you change the length of the resistor, how does a. the resistance change? (answer, explain, evidence) Evidence is shown above in one of my screenshots. When I increased the length of the wire, the resistance increased as well. b. the current through a circuit change? (answer, explain, evidence) The current decreases as the length of the resistor increases which then increases the resistance amount. Increasing the cross-sectional area will decrease the resistance and increase the current. 4. If you change the resistivity of the resistor, is the effect like changing the length or changing the area? (answer, explain, evidence) The resistivity of the resistor doesn’t depend on change of length or change of the area. 4/2/20 Loeblein https://phet.colorado.edu/en/contributions/update-success/5435 page 2
5. During manufacturing, how is the resistivity of a resistor changed? Cite your references During manufacturing, the resistivity of a resistor is changed through pattern. Manufacturers increase the resistance by cutting a pattern into the film in order to increase the path of the electrical current. https://eepower.com/resistor-guide/resistor-fundamentals/electrical-resistivity/# 6. Consider the two circuits below in which the left resistor is and the right one 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 I closed the switch, the lightbulb lit. When the switch is open, the lightbulb is off. b. How do you think the lights’ brightness will compare? The light’s brightness is best when the switch is closed. The closed switch causes less resistance and the current is higher. c. Open the Intro screen 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. 4/2/20 Loeblein https://phet.colorado.edu/en/contributions/update-success/5435 page 3
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