Electricity and Magnetism Physics Farmington High School Science Department

Transcription

1 Electricity and Magnetism Physics Farmington High School Science Department Farmington Public Schools Science Department Physics Author(s) Joanne White DRAFT: Farmington Public Schools 1

2 Table of Contents Unit Summary....page 3 Stage One: Standards Stage One identifies the desired results of the unit including the broad understandings, the unit outcome statement and essential questions that focus the unit, and the necessary knowledge and skills. The Understanding by Design Handbook, pages 4-7 Stage Two: Assessment Package Stage Two determines the acceptable evidence that students have acquired the understandings, knowledge and skills identified in Stage One. pages 8-12 Appendices A & B.... page 13 Author(s) Joanne White DRAFT: Farmington Public Schools 2

3 Unit Summary This unit, entitled Electricity and Magnetism, is a six week unit designed to be used in all introductory Level 2 and Level 3 physics courses at Farmington High School. Students in these classes include all freshmen and some juniors and seniors. This unit will be taught in the second semester of the academic year, either before or after a unit on Waves, Sound and Light. The unit focuses on static electricity and electric force; current electricity and circuits; and magnetism and its practical applications. Stage One: Standards Author(s) Joanne White DRAFT: Farmington Public Schools 3

4 Essential Understandings and Content Standards List the essential understandings and content standards which the unit or course addresses. Asterisk the content standards that are addressed by the performance task. These can be found in the K-12 standards document for your discipline. ESU #4 The behavior of the physical world can be interpreted, understood and predicted in terms of a few fundamental principals. The student will: 4.16 Interpret and make predictions about the physical world by utilizing the conservation principles. A. describe various forms of energy including mechanical, heat, light, electrical, and chemical energy, and identify them in various physical settings. E. illustrate the principle of conservation of charge Interpret and make predictions about the physical world by understanding the properties and behaviors of electric charge. A. explain that the electric force which exists between every two charges is either attractive or repulsive, and its strength is proportional to the product of the charges and inversely proportional to the square of the distance between the charges. B. recognize that charge is a property of all matter, and describe the charge characteristics of protons, neutrons and electrons. C. describe the effects of voltage and resistance on the flow of electric charges in series and parallel circuits. D. explain that magnetism and all magnetic effects arise from the relative motions of electric charges. E. describe how the interplay of electric currents and magnetic forces are the basis for motors, generators and modern electronic technologies. ESU #1 Scientific inquiry is an ongoing process building knowledge about events and phenomena. The student will: 1.23 distinguish between scientific statements, which can be tested, and non-scientific activities distinguish different reasons for conducting experiments, including exploration of new phenomena, checking previous results, and testing how well a theory predicts the behavior of nature frame, hypothesize, design, conduct, analyze and communicate and defend the results of a controlled experiment understand that all measurements are uncertain to some extent discuss the validity of experimental results evaluate a theory by how well it explains observations and how effective it is in predicting new findings. ESU #2 Science is a human endeavor which has lasting impact on civilization. Author(s) Joanne White DRAFT: Farmington Public Schools 4

5 The student will: 2.19 recognize that science is a community activity in which results are shared and evaluated amongst peers explain that curiosity, honesty, openness and skepticism are highly regarded in science and those they are incorporated into the way science is conducted recognize that progress in all fields of science is built upon knowledge and understandings attained through the work of previous scientists analyze how scientific advances have resulted in new benefits and new risks. ESU #9 Constancy, patterns, change and evolution permeate all systems. The student will: 9-14 use equations to describe how one quantity changes when another changes interpret trends and evaluate patterns of change using tables, graphs, and equations formulate predictions based upon identified patterns analyze changes that are so fast that they are difficult to detect. Math ESU #1 Students will understand that people use numbers to count, measure, compare, order, scale, locate and label, and that they use a variety of numerical representations to present, interpret, communicate, and connect various kinds of numerical information. The student will: 1c. develop and use an intuitive sense of number magnitude of numbers (including very large and very small numbers) and relate them to place value and exponential form. Technology Standard #3 Technology can assist with the statistical analysis of data as a powerful means for explaining, understanding, and predicting issues of the human condition or physical world. The student will: A. formulate sophisticated questions, extract data from surveys, research materials, or experiments and present it in well organized tables. B. present complex data in appropriate charts and graphs in a meaningful way. C. analyze data sources, identify relationships, select and apply appropriate statistical operations or transformations and draw conclusions. Author(s) Joanne White DRAFT: Farmington Public Schools 5

6 Unit Outcome Statement As a result of this unit on Electricity and Magnetism, students will know and understand that charge is a fundamental property of all matter, which produces electric forces. Students will also understand that moving charges can produce currents and magnetic fields. They will construct and analyze simple series and parallel circuits and understand the practical applications of electromagnetic technology in their own lives. Essential Questions How does the basic structure of the atom explain the electric and magnetic properties of matter? What is electric energy? If energy is always conserved, then how can electric energy be produced and destroyed? Author(s) Joanne White DRAFT: Farmington Public Schools 6

7 Knowledge and Skills Knowledge The Knowledge and Skills section includes the key facts, concepts, principles, skills, and processes called for by the content standards and needed by students to reach desired understandings. The Understanding by Design Handbook, 1999 Locate the electrons, protons and neutrons in the atom Calculate the electric force between charges using Coulombs Law Specify the direction of the force acting between charges Explain charging by friction, contact and induction Draw conceptual pictures of electric fields surrounding charges and groups of charges Use of Ohm s law in calculations Solve series and parallel circuits for resistance, voltage and currents Use of power formula for electrical components Analyze energy costs associated with electrical appliances Explain the cause of magnetism for permanent magnets and around electric currents Draw conceptual pictures of magnetic fields about permanent magnets and magnetic currents Use the left or right hand rule for determining the direction of the magnetic field Use the equation F=qvB to find the amount of magnetic force Explain how motors, generators and transformers work Skills/Processes Use of electric metric units. Measurement skills using ammeters and voltmeters. Connecting electrical items to form a complete circuit Recognition and reporting of the limits of precision and accuracy of measurements. Appropriate statistical analysis of data. Basic calculator use and use of scientific notation Problem solving skills and strategies. Creating appropriate data tables and graphs. Thinking Skills Making predictions Application of formulas and skills to unique problems. Interpret line graphs of motion Making inferences in lab inquiries Identifying valid experiments Draw valid conclusions Reflection and analysis of experimental data and experimental errors. Author(s) Joanne White DRAFT: Farmington Public Schools 7

8 Stage Two: Assessment Package Stage Two determines the acceptable evidence that students have acquired the understandings, knowledge and skills identified in Stage One. Authentic Performance Task Let s Conserve Energy! Goal The goal is to emphasize to students that energy is conserved. In this case from light to electricity to useful forms in their lives. They will transfer their knowledge of connecting resistors in series and parallel to connecting solar cells in series and parallel. They will also show that they have mastered setting up a circuit including meters and can accurately read and interpret the meters. Lastly, students will demonstrate their understanding of power and energy in order to perform a cost analysis. Role The students will be in the role of a typical home owner that would like to research the feasibility of using solar energy to supplement the electrical energy purchased from the power company. Audience The audience will be a bank loan officer. They need to convince the loan officer that this technology will eventually save them money and is a worthy investment for a home owner s loan or it will be too costly to use in Connecticut. Situation This task is designed to give students the opportunity to design and perform an experiment to gather data on photovoltaic cells (solar cells) connected in series and parallel, and then use the data collected to perform a cost analysis for using this technology in a typical Connecticut home. The students will then produce a report with their recommendations. There is an additional component of the cost analysis for level 2 classes to complete. Product/Performance and Purpose They will use their knowledge they have gained in connecting resistors in series and parallel and in reading ammeters and voltmeters to analyze the current and voltage when photovoltaic cells are connected in series and parallel. They will use their knowledge of how houses are wired and the power equation to figure out energy consumed by an average Connecticut home and then perform a cost analysis for installing and using solar technology in Connecticut. Each lab group will be given an ammeter, voltmeter, light bulbs, two PV cells and wires. They will also be given some preliminary information on PV cells and a worksheet to help them figure out the typical Connecticut household energy usage. They will be given information on the solar insolation for Connecticut, the cost of each PV cell. Students must research the typical cost of electric energy if purchased from the power company at present and make a reasonable assumption of the cost 10 years into the future. To successfully complete the task, the students must: a. realize that the PV cells must be connected to each other in groups of series and parallel arrays to meet the household requirement. b. Find the average daily household energy requirement in watt-hours. c. Determine the hours per day of available sunlight at the site. d. Determine the PV array size needed. e. Calculate the cost of the array. f. Write a loan request report that includes all information investigated. Additional Level 2 Tasks: a. calculate the cost of the same energy usage if purchased through the power company. b. find how long it will take the homeowner to break even using this technology over being connected to the utility grid. c. In the economic analysis, include the cost an inverter to change d.c. to a.c. current. d. The report should make a determination about whether this technology is economically feasible in Connecticut. Let s Conserve Energy Author(s) Joanne White DRAFT: Farmington Public Schools 8

9 Introduction We already learned that energy is always conserved. But can we conserve fossil fuels such as oil and coal and still have all of our modern conveniences such as heat, air conditioning, microwaves, stereos and computers? Is there another way that we can supply our energy needs in Connecticut without high utility bills? There is a free source of energy the Sun! It produces light, another form of energy. Even though the energy is free, the technology is not! Is it economically feasible to use sunlight to produce electrical energy in Connecticut? The Task It is 10 years from now and you are a homeowner that is tired of the high utility bills that you pay every month to the electric company. While browsing the web, you notice a pop-up add for a renewable energy source-solar energy. You decide to pursue this idea and research the requirements, how it is used and if it is cost efficient here in Farmington. You download many resources and have them attached. You need to read through the documents, calculate your household electricity requirement, set up and test to see how many photovoltaic cells (solar cells) that you need to meet your household requirement and if they should be connected in series or parallel or a combination of both. You will then conduct a cost analysis for purchasing solar cells. Finally, you will write up a report which you will use to convince a bank loan manager to finance this project The Report You report should include: Your household energy requirement and any backup evidence to prove your claim. Your results of tests on the PV cells in series and parallel and how many cells would be needed. Estimation of the PV system needed and the cost of the system. The size and location of your system at your home Your request to the loan officer. Additionally for level 2: Actual cost of purchasing electricity through the power company and the break even point in terms of years. A determination of whether the technology is economically feasible. If the project is not feasible or cost efficient, you must include your findings in a report to the loan officer and decline the financing. Author(s) Joanne White DRAFT: Farmington Public Schools 9

10 Connecticut Insolation Values by Month Month Insolation Value (KWH/m2) January 2.4 February 2.9 March 3.2 April 3.6 May 3.9 June 4.3 July 4.2 August 3.9 September 3.6 October 2.9 November 2.1 December 1.9 Author(s) Joanne White DRAFT: Farmington Public Schools 10

11 Testing PV Cells Constructing the Photovoltaic Energy system for Light Source Changes 1. Attach an ammeter and voltmeter to one of the PV cells. Use sun or shine a bright light on the PV cell to see if you are getting current and voltage readings. Record. 2. Keeping the light source and the distance to the light source constant, shade parts of the PV cell with a piece of cardboard. Record your results each time. 3. Point the PV cell directly at the sun or light source, and then vary the angle. Record you results. Connecting Multiple PV cells 1. Join the first PV cell to another PV cell in series under the same light source as before. Record your results. 2. Connect the two PV cells in parallel and record you results. Thought Questions 1. What happens to the amount of electricity generated when the PV cells are installed in the shade? 2. What happens to the amount of electricity generated when the angle of the PV cells to the sun changes daily or yearly? 3. How would you connect the PV cells so that your household requirement of 110 volts and 10 amps is supplied? 4. Where would you place these PV cells on your home for maximum electricity generation and safety? Student Name: Date: Author(s) Joanne White DRAFT: Farmington Public Schools 11

12 Physics Performance Assessment Scoring Rubric Title: Let s Conserve Energy Opening Sentence: The statement is (Maximum: 3 pts) 0 1 prominently stated 0 1 clear 0 1 succinct Display of Data: The data is (Maximum: 3 pts) 0 1 properly expressed (clarity, units, headings, significant figures ) 0 1 complete (all the necessary data) 0 1 relevantly chosen (data pertains to task) Calculations: The calculations (Maximum: 3 pts) 0 1 are accurately performed 0 1 are easy to follow 0 1 have answer(s) with proper units and significant figures Prediction: The prediction is (Maximum: 9 pts) easy to follow supported by thorough logic (contains everything the reader needs to know) appropriately accurate (within acceptable range of experimental error) Reflection: The conclusion or discussion section includes (Maximum: 8 pts) a final justified request for the loan identification of appropriate sources of error and assumptions Limitations of PV cell technology discussed Conclusion matches data Overall Presentation: The overall presentation of the report was (Maximum: 4 pts) neat, well organized, and easy to follow convincing Overall Rating: 30 Above Standard (26 30) At Standard (20 25) Near Standard (15 19) Below Standard (0 14) Author(s) Joanne White DRAFT: Farmington Public Schools 12

13 Additional Assessments Tests (See Appendix A) Test on Static Electricity Test on Current Electricity Test on Magnetism and Electromagnetism Labs and Projects: (See Appendix B) Internet Lab on Static Electricity Ohms Law Lab Series and parallel Lab Cost of Electricity Worksheet Build your own motor Author(s) Joanne White DRAFT: Farmington Public Schools 13