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Subject: Physics Timeframe Needed for Completion: 14 days Grade Level: 11,12 Unit Title: Unit 8: Electricity Grading Period: 2nd 9wks New 2009 goals are in red Big Idea/Theme: Static and Current Electricity Understandings: Students will understand how static electricity if produced. Students will understand how the electroscope works. Students will understand how series and parallel circuits conduct electricity. Students will understand voltage, amperes and electrical resistance in combination circuits. Curriculum Goals/Objectives (to be assessed at the end of the unit/quarter) Essential Questions: Why do we get shocked in the winter when 3.1.1 Explain qualitatively the fundamental properties of the interactions of charged objects. touching metal objects? • Identify basic principles related to the nature of electrical charge – like charges repel How is electricity produced? and opposite charges attract; there are two types of electric charge (positive and What is an electrical circuit? negative); positively charged objects have an electron deficiency while negatively What is lightning? charged objects have an excess of electrons. • Conclude that charge is conserved in a closed system – since charge is a result of fundamental properties of particles, charge (like atoms) cannot be created nor destroyed. 3.1.2 Explain the geometries and magnitudes of electric fields. • Construct diagrams to illustrate electric fields and explain its vector nature: around single positive and negative charges, between a pair of like charges, between a pair of unlike charges, two oppositely charged parallel plates, a hollow sphere, an irregular shaped metal object. • Compare the strength of various points in an electric field where and for a point charge for the uniform electric field between parallel plates. VEd= • Distinguish between charge distribution on plates and a hollow conducting sphere where no electric field exists inside. 3.1.3 Explain how Coulomb’s law relates to the electrostatic charged objects. interactions among • Conceptually and mathematically explain electrical attraction and repulsion using Coulomb’s law - the electrical force is directly proportional to the product of two charges and inversely proportional to the square of the distance between them, . 122ekqqFd= • Determine the magnitude and direction of an electric force between two charges. 3.1.4 Explain the mechanisms for producing electrostatic charges including charging by friction, conduction, and induction. Explain situations where objects become charged (by friction, conduction or induction) in terms of the transfer or rearrangement of electrons: • two neutral objects charged by friction, • a neutral object becoming positively charged by induction and conduction, • a neutral object becoming negatively charged by induction and conduction. 3.1.5 Explain how differences in electrostatic potentials relate to the potential energy of charged objects. • Compare work done on an object by lifting (changes in location in a gravitational field) to work done on a charged particle by pushing it against the electric field of a charged object – both positive and negative. • Define electric potential energy as the energy of a charge based on its location and distinguish electric potential (voltage) as being the same for all charges. • Conclude that a gravitational field is always in one direction while electric fields have two possible directions; by convention, the direction is determined by the direction of force on a positive test charge – away from (out of) a positive charge and toward (into) a negative charge. 2.3.1 Explain Ohm’s law in relation to electric circuits. • Recognize that a difference in potential (voltage) creates current within a conductor; the amount of current also depends on the resistance of the conductor. • Develop a cause-and-effect model for current in a circuit - current is directly proportional to the voltage and inversely proportional to the resistance (Ohm’s law), • Given a schematic circuit diagram, determine current, voltage, or resistance from two known quantities. 2.3.2 Differentiate the behavior of moving charges in conductors and insulators. • Identify conductors as materials that have electrons that are free to move throughout the sample; Metals are good conductors of electrical charge. • Identify insulators as materials where electrons are held tightly to individual nuclei; Rubber and glass are examples of insulators that because of their properties develop static charge readily through friction with other materials. • Explain classification as a conductor or insulator based on the ability of electric charge to move through the material. 2.3.3 Compare the general characteristics of AC and DC systems without calculations. Compare alternating and direct current systems based on the source of electrical energy, transmission over distances, ease of use in varied electrical devices, etc. 2.3.4 Analyze electric systems in terms of their energy and power. • Develop the concept of power using dimensional analysis (unit cancellation) where electrical power can be calculated from current, voltage and/or resistance measurements, • Since power is defined as the rate of work done or energy transferred, energy used by a device can be calculated by multiplying power and time, 2.3.5 Analyze systems with multiple potential differences and resistors connected in series and parallel circuits, both conceptually and mathematically, in terms of voltage, current and resistance. • Analyze series circuits to distinguish the following patterns for current, voltage, and equivalent resistance: • Analyze parallel circuits to distinguish the following patterns for current, voltage, and equivalent resistance: current through each device equals the current supplied each branch is the same reciprocals, (Equivalent resistance in a parallel arrangement is lower than any one resistance in the arrangement.) • Conclude that multiple potential difference (voltage) sources are additive when arranged in series; current moving from positive to negative constitutes a negative potential difference. (e.g. - Two six volt batteries in series connecting positive to negative terminals have a combined potential difference of twelve volts; a six volt battery in series connecting positive to positive terminals with a three volt battery would establish a combined potential difference of three volts.) Network circuits where a second emf is located in a branch should not be included in the standard level course. • Analyze series-parallel combination circuits by determining equivalent resistance of portions of the circuit until it can be reduced to a simple series or parallel circuit. Essential Skills/Vocabulary: Conduct investigations involving static electricity. Analyze the nature of electrical charge. a. The two different kinds of electric charge are defined as positive and negative. b. Like charges repel and unlike charges attract. Understand that matter is neutral when charges are balanced and becomes charged when there is a transfer of electrons. Recognize the three methods of charge transfer are friction, conduction, and induction. Understand that electric charge is conserved (neither created nor destroyed and may be transferred from one object to another). Calculate the electrostatic force between any two point charges using the equation: kq1 q2 F d2 Apply the inverse square relationship between the force and the distance between the charges. Apply the proportional relationship between the force and the product of the charges. Cite evidence from experiments to support the existence of two kinds of charge, the neutrality of most matter, and explain charging by friction, conduction and induction. Apply Ohm’s Law: V IR o Solve simple circuit problems. Assessment Tasks: Major test, quizzes, homework Lab on Series Circuits Lab on Parallel Circuits Lab on Combination Circuits Website on Electricity and Building Circuits Rotational Lab (Students rotate around 6 lab tables and observe electrical phenomena) http://www.ncpublicschools.org/curriculum/science/scos/2004/27physics ( FOR SUPPLIES NEEDED TO ACCOMPANY THE BELOW “INQUIRY SUPPORT LABS”) Electrostatic lab-investigating electrostatics using common household items such as making an electroscope from cellophane tape, balloons or pie pans Inquiry Support Lab: Sticky Tape Lab Current and resistance lab Inquiry Support Lab: Circuit Activity Inquiry Support Lab: Verifying Ohm’s Law Inquiry Support Lab: Ohm’s Law Activity Inquiry Support Lab: Current and Voltage for Resistors in Series, Parallel, and Mixed Circuits Inquiry Support Lab: Voltage Activity o Graph results from investigations. Observe how potential difference, current and resistance affect the brightness of light bulbs in circuits with batteries. Design and conduct investigations to measure potential difference and current in direct current circuits with resistors and batteries. Series circuits Recognize that current is the same throughout the circuit: I t I 1 I 2 I 3 ... Recognize that voltage divides proportionally to the resistance. The sum of the voltage drops across the circuit equals the potential difference supplied to the circuit: Vt V1 V2 V3 ... Calculate equivalent resistance: R eq R1 R 2 R 3 ... Apply Ohm’s law to series circuits. Parallel circuits Recognize that current divides in inverse proportion to the resistance. The sum of the current through each device equals the current supplied to the circuit: I t I 1 I 2 I 3 ... Recognize that the voltage drop across each branch is the same: Vt V1 V2 V3 ... Calculate equivalent resistance: 1 1 1 1 ... R eq R1 R 2 R 3 Apply Ohm’s law to parallel circuits. Combination circuits Calculate equivalent resistance. Develop a conceptual understanding of voltage and current in a combination circuit. AC/DC Systems Calculate and compare alternating and direct current systems based on the source of electrical energy. Materials Suggestions: http://www.ncpublicschools.org/curriculum/science/scos/2004/27physics ( FOR SUPPLIES NEEDED TO ACCOMPANY THE BELOW “INQUIRY SUPPORT LABS”) Transparent tape Soda can Styrofoam cup. Dry cell Wire flashlight bulb 10 watt power resistors 6- 1.5 V dry cells Ammeter Voltmeter One variable voltage DC power supply, one ammeter and one voltmeter (or two multimeters) per group of 2 – 4 students. Various resistors. Various connecting wires. Graphing software. 21st Century Skills Communication Skills Conveying thought or opinions effectively When presenting information, distinguishing between relevant and irrelevant Activity Analysis questions in all labs Data collection in all Lab Activities information Explaining a concept to others Sign Off—Sticky Tape lab Circuit Activity Ohm’s Law activity Sign Off—Sticky Tape lab Circuit Activity Interviewing others or being interviewed Computer Knowledge Using word-processing Making graphs in labs and database programs Developing visual Sticky Tape Lab aides for presentations Using a computer for Sticky Tape communication Ohm’s Law Activity Learning new software Circuit Web link programs Employability Skills Assuming Sticky Tape responsibility for own Activities learning Sign Off –Circuit & Ohm’s law Activity Persisting until job is completed Working independently Sticky Tape Developing career interest/goals Responding to Sign Off –Sticky Tape criticism or questions Ohm’s Law Information-retrieval Skills Searching for Voltage Activity information via the computer Searching for print information Searching for information using community members Current and Voltage for Resistors in Series & Parallel Current and Voltage for Resistors in Series & Parallel Language Skills Reading Following written directions Identifying cause and effect relationships Summarizing main points after reading Locating and choosing appropriate reference materials Reading for personal learning Language Skill Writing Using language accurately Organizing and relating ideas when writing Proofing and Editing Synthesizing information from several sources Documenting sources Developing an outline Writing to persuade or justify a position Creating memos, letters, other forms of correspondence Teamwork Taking initiative Working on a team Thinking/Problem- Most of the activities can be presented as opportunities for students to follow written directions. The teacher will have to work with most students to develop this skill over time. Sticky Tape Ohm’s Law All lab activities “Explain” and “Evaluate” sections in all lab activities Current and Voltage for Resistors in Series & Parallel Sign Off Activity Sign Off Activity All lab activities Sign Off Activity All lab activities Sign Off Activity Solving Skills Identifying key problems or questions Evaluating results Developing strategies to address problems Developing an action plan or timeline All lab activities Sign Off Activity All lab activities Sign Off Activity