Copy_of_PHYS140_RC_Circuits_Lab_-_STUDENT_VERSION_(Graphical_Analysis)

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Siena College *

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Apr 3, 2024

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Siena College - General Physics 140 RC Circuits Lab NAME: GROUP MEMBERS: Learning Goals 1. In Section I, you will identify the conditions necessary to allow for a continuous flow of electric charge by observing and explaining patterns that occur when two objects at different electric potentials (a Van de Graaff generator and its grounding rod) interact with a third object. 2. In Section II, you will construct an idea of what constitutes a complete circuit by observing and explaining patterns involving the arrangement of circuit elements that make a lightbulb glow. 3. In Section III, you will investigate the charging and discharging of a capacitor from an electric charge perspective. 4. In Section IV, you will investigate the charging and discharging of a capacitor from an energy perspective. Driving Question(s): What conditions are necessary to allow for the continuous flow of electric charge in an electric circuit? How can a charge separation be maintained so that electric potential energy can be stored for eventual uses? In a resistor-capacitor (RC) circuit, how can a capacitor prevent or allow a lightbulb to illuminate? Section I - In this part of the lab, you will identify the conditions necessary to allow for a continuous flow of electric charge by observing and explaining patterns that occur when two objects at different electric potentials (a Van de Graaff generator and its grounding rod) interact with a third object. Equipment: Van de Graaff generator with grounding rod, aluminum foil ball hung from an insulated thread, long fluorescent lamp. Scientific Ability Missing Inadequate Needs Improvement Adequate B7 Is able to identify a pattern in the data No attempt is made to search for a pattern. The pattern described is irrelevant or inconsistent with the data. The pattern has minor errors or omissions. The pattern represents the relevant trend in the data. B9 Is able to devise an explanation for an observed pattern No attempt is made to explain the observed pattern. An explanation is vague, not testable, or contradicts the pattern. An explanation contradicts previous knowledge or the reasoning is flawed. A reasonable explanation is made. It is testable and it explains the observed pattern. Your instructor charges a Van de Graaff generator while its grounding rod is close to, but not touching the Van de Graaff. While this is happening, an aluminum foil ball is hanging from a thin thread made of insulating material and is already 1

Siena College - General Physics 140 RC Circuits Lab positioned in between the Van de Graaff and the grounding rod. The aluminum foil ball is allowed to move freely. After several seconds, the generator is turned off and the aluminum foil ball is still allowed to move freely based on its interactions with the Van de Graaff and the grounding rod. Answer the following questions with your group. A. Record your observations. What happened to the aluminum foil ball? The aluminum foil moves initially because of the electrostatic forces and it eventually settles into static equilibrium due to the charge distribution generated by the Van de Graaff generator. B. Explain why you observed what you did by describing all the energy conversions that took place when the ball moved from one sphere to the other and back again. Explain your thinking as to why you expect or don’t expect this motion to continue indefinitely. As the generator becomes positively charged it induces an opposite charge on the aluminum foil ball hanging. The repulsive force between like charges causes the aluminum foil to experience a force away from the positively charged dome of the generator and moves towards the grounding rod. The kinetic energy of the ball is partially converted to potential energy as it moves closer to the grounding rod. C. Explain why you observed what you did by using a microscopic model of charging and using the concept of electric potential. The generator builds up a high electric potential on its dome due to the accumulation of positive charge. The grounding rod being grounded maintains a lower electric potential but with an opposite charge distribution. Your instructor charges a Van de Graaff generator and places its grounding rod close to, but not touching the Van de Graaff. Then, each end of a fluorescent lamp is allowed to touch either the generator or the grounding rod. Answer the following questions with your group. D. Record and explain your observations by using the ideas you developed in the previous experiment. How is this similar to and different from the case of the aluminum foil ball? Once the lamp loses contact with either the generator or the grounding rod it stops emitting light. The lamp only remains light while in contact with the generator and grounding rod. In both experiments there’s positive charge around the dome. E. Explain why the flash of light lasts for such a short time interval. The flash of light only lasts a short amount of time because it is a result of the 2

Siena College - General Physics 140 RC Circuits Lab rapid discharge of stored electrical energy in the lamp’s tube . Section II - In this part of the lab, you will construct an idea of what constitutes a complete circuit by observing and explaining patterns involving the arrangement of circuit elements that make a lightbulb glow. Equipment: Batteries, lightbulbs, wires. Scientific Ability Missing Inadequate Needs Improvement Adequate A7 Sketch No representation is constructed. The sketch is drawn, but it is incomplete with no physical quantities labeled, or important information is missing, or it contains wrong information, or coordinate axes are missing. The sketch has no incorrect information, but has either no or very few labels of given quantities. Subscripts are missing or inconsistent. The majority of key items are drawn. The sketch contains all key items with correct labeling of all physical quantities that have consistent subscripts; axes are drawn and labeled correctly. B5 Is able to describe what is observed without trying to explain, both in words and by means of a picture of the experimental setup No description is mentioned. The description is incomplete. No labeled sketch is present. Or, observations are adjusted to fit expectations. The description is complete, but mixed up with explanations or patterns. The sketch is present, but it is difficult to understand. Clearly describes what happens in the experiments both verbally and with a sketch. Provides other representations when necessary (tables and graphs). You have a battery, two wires, and a lightbulb. Work with your group to try different arrangements of these four elements to make the lightbulb glow. Then, remove one wire and try to light the bulb with just a battery and one wire. A. Draw pictures of the arrangements that allow the bulb to light and several where it does not do so. Explain how this experiment is similar to the experiments in Part I and how it is different. 3

Siena College - General Physics 140 RC Circuits Lab Both experiments have a complete circuit and they both have a battery source. The first experiments electrons come from the ground but this one comes from the battery. B. Based on your successful arrangements when the bulb lit up, discuss the conditions that are necessary for a lightbulb to illuminate. There must be a potential difference and it has to be a closed circuit with conductive wires. There also needs to be a functional light source. C. Summarize the conditions that are necessary for the continuous flow of electric charge in an electric circuit. There needs to be a continuous flow of electric charge in the circuit and a battery charge. D. Construct an analogy to explain how an electric circuit works. Use the following table to help you create your analogy. Using your analogy, fill in the table below to identify the counterpart for each element of an electric circuit. Note: An analogy involves mapping between the target phenomenon (the one we are trying to understand) and some source phenomenon (that we understand and are using to compare to the target phenomenon). The source phenomenon should be some everyday experience that you are familiar with, and whose physical processes are similar to the workings of the electric circuit you’re trying to explain (this is your target phenomenon). Source Phenomenon Target Phenomenon (electric circuit) 4

Siena College - General Physics 140 RC Circuits Lab Water pump Battery Pipes Connecting wires Faucet Lightbulb Flow of water Electric charges E. Explain how your analogy works. How are the elements of your source phenomenon similar to the battery, connecting wires, lightbulb, and electric charges? The water pump is the battery because they both provide electrical potential difference. The pipes are the wires because they provide somewhere for the eclectic current to flow. The faucet is the bulb because when the water passes through water is able to come out the facet and cause a flow of water. Section III - In this part of the lab, you will investigate the charging and discharging of a capacitor from an electric charge perspective. Equipment: Demonstration capacitor of 25,000 μF, a circuit to charge and discharge the capacitor, light bulb to indicate the flow of charge, wires, batteries or a power supply, Graphical Analysis, Vernier Go-Direct voltage probe, a switch. Scientific Ability Missing Inadequate Needs Improvement Adequate B5 Is able to describe what is observed without trying to explain, both in words and by means of a picture of the experimental setup No description is mentioned. The description is incomplete. No labeled sketch is present. Or, observations are adjusted to fit expectations. The description is complete, but mixed up with explanations or patterns. The sketch is present, but it is difficult to understand. Clearly describes what happens in the experiments both verbally and with a sketch. Provides other representations when necessary (tables and graphs). A11 Graph No graph is present. A graph is present, but the axes are not labeled. There is no scale on the axes. The data points are incorrectly connected to each other instead of using an appropriate trendline. The graph is present and the axes are labeled, but the axes do not correspond to the independent and dependent variable OR the scale is not accurate. The data points are not connected to each other, but there is no trendline either. The graph has correctly labeled axes, the independent variable is along the horizontal axis and the scale is accurate. The trendline is correct. 5

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