lab assigment
College Physics II Electrostatics: Electric Field and Conductors EPCC Part 1: Coulomb Forces Goal: This lab will demonstrate electrostatic forces (Fe) and electric fields (E). Supplies: Aluminum can, metric ruler, pencil/pen, cloth, plastic object or other prescribed item. Note: Measurements must be in MKS units. Understanding charges Objects can gain and lose static charge. Figure 1 describes a few materials that carry certain types of charge. Coulomb’s Law (Refer to figure 2): • Place and fasten a metric ruler on a table. Align the middle an empty aluminum soda can at the 15.0 cm mark (figure 2a). • Sketch a full, detailed free body diagram of can on a separate sheet of paper (i.e. horizontal and vertical forces). • Charge an object with some cloth; see figure 2b. • Slowly bring the charged object closer to the aluminum can (figure 2c). Note the distance between the charged object and the can when the can begins to move. Record this reaction in table 1. • Calculate the Coulomb force acting on the system by deriving the equation based on your free body diagram. Record your results in table 1. For your calculations assume the following: The coefficient of static friction (µs) to be 0.20 and the amount of charge on the can is the same as on the charged object. Figure 1: Information on electrostatic charges and materials. (a) (b) (c) Figure 2: Laboratory part 1 set up for determining the Coulomb force strength. College Physics II Electrostatics: Electric Field and Conductors EPCC Table 1. Object name Mass (kg) Normal force (N) Reaction distance (m) Coulomb force (N) Charge on can (C) 0.0149 Questions (answer concisely within 3 sentences): 1. Based on your results and observations, what was the charge (i.e. + or -) of both the can and the charged object? How do you justify your conclusions? 2. Based on your laboratory experience, how can you ascertain the physical characteristics/ composition of the materials used here? Part 2: Electric fields Goal: Understand electric fields as “fields of influence”. Supplies: Pencil, calculator, paper, ruler, results from part 1. Procedure (Refer to figure 3): Mark a point in the middle of a blank sheet of paper. This will represent the can placed at that point. Using the reaction distance recorded in table 1, mark a spot that distance away from your midpoint (Figure 3a). Using a compass or other drawing device, draw a circle that hits that point you made (figure 3b). Next draw another circle with twice the radius as the first. Label those distances on the paper (figure 3c). At each circle, calculate the electric field and the Coulomb force that another similar can would experience. (a) (b) (c) Figure 3: Examples of electric fields and forces. (a) measuring out the distance where the can from part 1 experienced initial movement, i.e. at 2.0 cm. (b) A circle representing radial distances of 2.0 cm from the source where the electric field measured there would be uniform. (c) another circle twice the distance as the first representing another region of uniform but weakened electric field. College Physics II Electrostatics: Electric Field and Conductors EPCC Questions (answer concisely within 3 sentences). 1. Based on your calculations, what happens to the electric field and force as you go further away from the source? 2. Pick an arbitrary point along the first circle and calculate the electric field there. What can you determine about the electric field along that first circle? The second one? Part 3: Properties of conductors. Review the sections in your book regarding properties of conductors: Conductors and insulators: https://openstax.org/books/college-physics/pages/18-2-conductors-and-insulators Charges on a conductor: https://openstax.org/books/college-physics/pages/18-7-conductors-and-electric-fields-in-static- equilibrium Questions (respond within 3 sentences) 1. Watch the video: https://www.youtube.com/watch?v=LfJywoeIIUI What can you say about the force experience by the charge inside the sphere? 2. What is an electric field and electrostatic force? How are they different? https://openstax.org/books/college-physics/pages/18-2-conductors-and-insulators https://www.youtube.com/watch?v=LfJywoeIIUI https://openstax.org/books/college-physics/pages/18-7-conductors-and-electric-fields-in-static-equilibrium https://openstax.org/books/college-physics/pages/18-7-conductors-and-electric-fields-in-static-equilibrium College Physics II Electric Potential and Potential Energy EPCC Part 1: Coulomb Forces Objective: This lab will demonstrate electrostatic forces (Fe) and electric fields (E) for further study on electric potential energy (Ue) and electric potential (V). Supplies: Aluminum can, metric ruler, pencil/pen, cloth, plastic object or other prescribed item. Note: Measurements must be in MKS units. Understanding charges Objects can gain and lose static charge. Figure 1 describes a few materials that carry certain types of charge. Coulomb’s Law (Refer to figure 2): • Place and fasten a metric ruler on a table. Align the middle an empty aluminum soda can at the 15.0 cm mark (figure 2a). • Sketch a full, detailed free body diagram of can on a separate sheet of paper (i.e. horizontal and vertical forces). • Charge an object with some cloth; see figure 2b. • Slowly bring the charged object closer to the aluminum can (figure 2c). Note the distance between the charged object and the can when the can begins to move. Record this reaction in table 1. • Calculate the Coulomb force acting on the system by deriving the equation based on your free body diagram. Record your results in table 1. For your calculations assume the following: The coefficient of static friction (µs) to be 0.20 and the amount of charge on the can is the same as on the charged object. Figure 1: Information on electrostatic charges and materials. Figure 2: Laboratory part 1 set up for determining the Coulomb force strength. College Physics II Electric Potential and Potential Energy EPCC Table 1. Object name Mass (kg) Normal force (N) Reaction distance (m) Coulomb force (N) Charge on can (C) 0.0149 Part II: Electric Potential Energy and Potential (refer to setup in part I and figure 3) • Charge an object again and place it at the 10.0 cm mark. • Place the can at the 0.00 cm mark. Slowly move the can closer to the charged object and test to see if it is attracted to the object. Continue doing this until when upon release of the can it moves automatically toward the object. Record this reaction distance in table 2. • Calculate the total electric potential energy and total electric potential. Determine the maximum kinetic energy and final velocity of the can. Record in table 2. • Repeat this using two charged object. Record the reaction distance in table 2. Table 2 # of Objects Reaction distance (m) Total Electric Potential Energy (J) Total Electric Potential (V) Maximum KE gained (J) Mass of can (kg) Vf of can (m/s) 1 0.0149 2 0.0149 Questions (answer concisely within 3 sentences): 1. How is the conservation of energy used here to determine the kinetic energy? 2. What is the difference between the electric potential and electric potential energy? 3. How can you increase the electric potential energy of this system? Figure 3: (a) Can 10.0 cm away from the charged object (yellow highlighter). Slowly move the can closer to the charged object, determining if there is any motion when free to move. (b) similar exercise only with two charged objects. College Physics II Electric Potential and Potential Energy EPCC Part 3: Electric Potential and Equipotential Lines Goal: Understand electric fields as “fields of influence”. Supplies: Pencil, calculator, paper, ruler, results from part 1. Procedure (Refer to figure 4): Mark a point in the middle of a blank sheet of paper. This will represent the charged object placed at that point. Using the reaction distance recorded in table 1, mark a spot that distance away from your midpoint (Figure 4a). Using a compass or other drawing device, draw a circle that hits that point you made (figure 4b). Next draw another circle with twice the radius as the first. Label those distances on the paper (figure 4c). At each circle, calculate the electric potential and the electric potential energy. Figure 4: Examples of electric fields and forces. (a) measuring out the distance where the charged object from part 2 experienced initial movement, i.e. at 2.0 cm. (b) A circle representing radial distance of 2.0 cm from the source where the electric potential measured anywhere along that circle would be uniform. (c) another circle twice the distance as the first representing another region of uniform but weakened electric potential. College Physics II Electric Potential and Potential Energy EPCC Questions (answer concisely within 3 sentences). 4. Label the regions of equipotential on your circle diagram. What happens to the electric potential the further away from the source you are? 5. How can you use the electric potential to determine how much electric potential energy you could have? 6. Figure 5 shows a contour map; where each line describes elevation. To learn more how to read a contour/topographical map, watch the video below: https://youtu.be/CoVcRxza8nI Referring to figure 5, calculate the potential energy between gained between points A and B going uphill if you had a mass of 100.0 kg. If you were to “fall” from A to B, what would be your kinetic energy gained? What would be your final velocity when you reach B? How does this topographical map’s contour lines relate to lines of equipotential? Assuming the can is negatively charge, will it move toward higher or lower electric potential? Explain your reasoning. Use your book and online notes (slide 41) to guide your analysis. A B Figure 5: A contour map of a mountainous region. (A) is assumed to be at an elevation of 1350 m, while (B) is at 1250 m. https://youtu.be/CoVcRxza8nI