Series And Parallel Combination

Series and Parallel Electric Circuits - Grade 11 Ohio Standards Connection Technology Designed World Benchmark A Classify, demonstrate, examine, and appraise energy and power technologies. Indicator 3 Use a series circuit and a parallel circuit to modify the voltage and current available from a group of batteries. Design Benchmark C Understand and apply research, development, and experimentation to problem solving. Indicator 1 Recognize identify, and apply the concept of function to solution of technological problems.

Lesson Summary: This lesson provides students opportunities for learning to construct and test simple series and parallel circuits. In addition, they learn to use such circuits to modify the voltage and current available from batteries. Ohm's Law and Kirchoff’s Current and Voltage Laws provide the basis of design. Class discussions, demonstrations and hands-on laboratory activities enable students to discover problemsolving techniques. Students will explore the advantages, disadvantages and applications of series circuits and parallel circuits, resulting in recognition and identification of functions for an array of solutions to technological problems. This lesson can be taught individually by a technology education teacher or in collaboration with mathematics and science teachers. Estimated Duration: Four days, 80-minute blocks Commentary: This lesson helps students learn the characteristics and benefits of series and parallel circuits. Students at this level should be well-acquainted with symbols representing resistors and voltage sources. Students should know all other electric symbols of components discussed in this lesson. (Provide a handout of all electric symbols discussed). An interdisciplinary approach bolsters the lesson. The mathematics teacher can review proportions and ratios to apply Ohm's Law and Kirchoff’s Current and Voltage Laws. A science teacher can cover electrical force and motion, to assist students in visualizing the flow of electrons to cause motion. The school library media specialist can share resources on electricity, electronics and careers in the field. The interdisciplinary approach helps students realize other subjects contribute to the topic discussed. Sharing with colleagues reinforces the student views of the interrelationship of subjects. The underlying questions throughout the investigations (exercises) include what design is best for a series circuit? What design is best for a parallel circuit? What are the consequences of such choices?

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Series and Parallel Electric Circuits - Grade 11 Pre-Assessment: • Students complete the pre-assessment, Attachment A. 1. Define electrons, current, voltage, resistance, load, Ohm's Law, open circuit and closed circuit. 2. Sketch a closed series circuit that includes a DC voltage source and a load (2 resistors). 3. Sketch a closed parallel circuit that includes a DC voltage source and a load (2 resistors). 4. List one application for a series circuit and one application for a parallel circuit. • Collect papers and discuss student responses in class. • Compare student responses to those provided in Attachment B, Pre-Assessment Answer Key. Scoring Guidelines: The pre-assessment identifies electronics basics students know to enable adequate preparation for the series and parallel circuit experiences. The pre-assessment activity promotes interest and curiosity for subsequent aspects of the lessons. Post-Assessment: • Review the vocabulary. • In teams of two complete Attachment I, Post-Assessment: Scoring Guidelines: The post-assessment shows the degree to which students have acquired the basic knowledge of series and parallel circuits. It also establishes student circuit building skills. Further, the post-assessment applies the concept of basic electronics to a virtual life application. Use Attachment J, Post-Assessment Guide – Sample Answers and Attachment K, Post-Assessment Rubric for Grading. Instructional Procedures: Day One Instructional Tip: A day prior to the first class, ask students to compile a list of uses for electricity in a home and compare them to the electrical usage in a car. Use this to stimulate thinking about the various applications and forms of electricity. In addition, ask students to sketch as many electric schematic symbols as possible. 1. Introduce the lesson by having students identify several electrical applications. • Discuss the variety of electrical needs and list student responses on the board. • Refer to assignments given prior to this class and discuss student findings about home electric usage versus car electrical usage. Review electrical circuits. Collect the

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Series and Parallel Electric Circuits - Grade 11 assignments after the discussion. Use the information to gauge class understanding, and review as necessary. • Ask whether floodlights on a playing field or a stadium use the same energy source as the cafeteria lights. Discuss how light intensities for both floodlights and cafeteria lights are achieved. • Discuss safety issues when dealing with electricity and electronics circuits. Cover personal dangers and proper ways to avoid them, equipment and tool safety and safety ethics, such as not tampering with electrical circuits without permission. 2. Administer the pre-assessment. 3. Brainstorm the challenges faced by designers of electrical systems in the distribution of current for different needs. Instructional Tips: • Show and explain different types of electrical loads, such as fixed and variable resistors, fixed and variable inductors, capacitors, diodes, transistors and integrated circuits. • Display Attachment C, Resistor Value Table, using an overhead display. • The necessary materials (e.g., resistors and batteries) should be labeled and prepared prior to Day One. 4. Discuss the need for resistors and their rating system (see Attachment C). Ask students when to use low beam or high beam headlights at night. Ask how switching from high beam to low beam and vice versa happens, considering both types use a constant voltage. 5. Demonstrate how to use a multi-meter to measure resistors, voltage and current. 6. Team students with a partner and distribute materials such as resistors, batteries, Attachment D, etc. 7. Have each team complete Attachment D, Exercises A, B & C in class. 8. Assign the following problem for homework: Students perform reverse engineering by asking parents or guardians to supervise students’ work while they locate and disassemble two electronic devices and trace their current flow. Students will sketch the electrical circuits and identify whether they are series or parallel circuits. Wherever possible, they should reassemble the electronic device to its original state or make a non-functioning device work if they can troubleshoot the problem. This assignment must be completed to discuss on the fourth day, before the post-assessment exercise. Day Two Instructional Tip: Attachment E, Series Circuit Analysis – Demonstrations and Attachment G, Parallel Circuit Analysis – Demonstrations serve as good platforms for introducing circuits. Be sure students learn voltage drop across each resistor, plus how to calculate and measure it. Kirchoff’s Voltage Law, which states that the sum of all voltage drops is equal to the voltage source, must be taught. Point out that only one current path exists in a series circuit. Derive Ohm's

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Series and Parallel Electric Circuits - Grade 11 Law using the current, voltage and resistor relationships. Use a flashlight with three dry cells as a good example of batteries connected in series with the correct polarity. 9. Review and discuss the previous class exercise on measurement and resistor identification. Seek responses on what they liked best and why, what they disliked and why and what they learned. 10. Introduce the series circuit. 11. Introduce Ohm's Law. 12. Introduce Kirchoff's Voltage Law. 13. Distribute Attachment E and explain the steps involved in series circuit analysis. 14. Have students record their results on Attachment F, Series Circuit Assignment and Recording Sheet. Instructional Tip: Note that the exercise heavily relies on instructor demonstration of building a series circuit. First, sketch the circuit, then build it on the breadboard. Students watch the interpretation of the schematic and translation of it onto the breadboard. Day Three Instructional Tip: Emphasize the difference between series and parallel circuits. Explain how Kirchoff's Current Law and the current divider rule apply. 15. Review the previous class exercise on series circuit. Discuss how to use scientific inquiry to determine whether to use a series circuit or parallel circuit. 16. Introduce the parallel circuit. 17. Introduce Kirchoff's Current Law. 18. Distribute Attachment G. 19. Demonstrate how to build a parallel circuit. 20. Have students record their results on Attachment H, Parallel Circuit Assignment and Recording Sheet. Day Four Instructional Tip: Discuss with students the challenges faced in building their circuits. Seek responses from students on how to overcome such challenges. Explain the exercise and administer the postassessment. 21. Review all previous class exercises. 22. Administer the post-assessment exercise, Attachment I. 23. Provide closure with a class discussion that focuses on the challenges students experienced in the design process and the strategies used to solve the problems. 4

Series and Parallel Electric Circuits - Grade 11 • •

Engage students in a discussion on how similar problem-solving techniques derived from scientific inquiry may be applied to manage real life problems. Involve them in peer evaluation of car speaker placements. See Attachment I, question three.

Differentiated Instructional Support: Instruction is differentiated according to learner needs, to help the learner meet the intent of the specified indicator(s) or if the indicator is already met, to advance beyond specified indicator(s). • Allow students showing evidence of working toward meeting the standard an opportunity to review any of the challenging information. Allow them to access exercises already done, such as measuring resistor values, building series and parallel circuits to strengthen their knowledge and gain confidence. • Include disassembly of simple electronic gadgets such as flashlights, nonfunctional computers and electronic children's toys in order to trace the current paths. • Allow students the opportunity to create their own design with available electronic components such as light and sirens. Use potentiometers to introduce the variable resistor. Extensions: • Develop concept designs for further electronic solutions for applications. Conduct exercises in electrical motor selection. Introduce formulas for motor selection and show at least three different motors: One with a greater torque; one for greater speed; and one in between. Show the computational outputs and ask students what an appropriate application would be for each motor. • Students use the Internet to access Web sites with electronic circuit designs and electrical and electronics simulations, particularly simulation of parallel and series circuits and motor selection and operation. Use the search terms Kirchoff's Laws, Kirchoff's Current and Voltage Laws, and Kirchoff's Rules to find Web sites with technical information, illustrations of circuits and animations. • Students keep a portfolio of sketches made as records of their design strategies. • Invite an electronic circuit designer and builder as a guest speaker to inform students about careers in the field. • Students use a spreadsheet software program to develop final data reports generated from their lab exercises. Interdisciplinary Connections: Science Scientific Inquiry Benchmark A Make appropriate choices when designing and participating in scientific investigations by using cognitive and manipulative skills when collecting data and formulating conclusions from the data.

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Series and Parallel Electric Circuits - Grade 11 Indicator 3 Design and carry out scientific inquiry (investigation), communicate and critique results through peer review. Materials and Resources: The inclusion of a specific resource in any lesson formulated by the Ohio Department of Education should not be interpreted as an endorsement of that particular resource, or any of its contents, by the Ohio Department of Education. The Ohio Department of Education does not endorse any particular resource. The Web addresses listed are for a given site’s main page; therefore, it may be necessary to search within that site to find the specific information required for a given lesson. Please note that information published on the Internet changes over time; therefore, the links provided may no longer contain the specific information related to a given lesson. Teachers are advised to preview all sites before using them with students. Note: Some Web sites contain material that is protected by copyright. Teachers should ensure that any use of material from the Web does not infringe upon the content owner's copyright. For the teacher: breadboard, fixed and variable resistors, capacitors, fixed and variable inductors, transistors, diodes, integrated circuits, jumpers, multi-meter, electronic device to project information on a screen, power supply, batteries, some board writing instrument (chalk or dry erase), electric schematic symbols. For the student:

breadboard, six fixed resistors, multi-meter, jumpers, voltage supply

Vocabulary: • amperage • electric circuit • electric current • Kirchoff’s Voltage Law • Kirchoff’s Current Law • load • Ohm's Law • polarity • resistance • symbols (resistor and voltage source) • voltage • voltage drop

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Series and Parallel Electric Circuits - Grade 11 Library Connections: In 2003, the State Board of Education and the Ohio Department of Education established library guidelines that represent a standards-based education approach to school library programs. Entitled Academic Content Standards K-12 Guidelines Library, Ohio’s library guidelines provide a variety of content-specific, grade-level indicators describing information literacy, literacy linked to library-based technologies, and media literacy experiences for students. Featured on pages 204-219 are sample activities for making library connections across academic content standards and disciplines. Also included are gradeband models for student research and specific information concerning copyright and fair use of materials laws. K-12 teachers are encouraged to utilize the library guidelines and collaborate with the school library media specialist whenever possible. Ohio’s library guidelines can be found under the heading of Library at www.ode.state.oh.us, keyword search Library. Library Technology Literacy Benchmark A Formulate advanced search strategies, demonstrating an understanding of the strengths and limitations of the Internet, and evaluate the quality and appropriate use of Internet resources. Indicator 2 Create a product on a specific curricular topic that includes annotated Web sites constructed according to a standard style manual (e.g., electronic pathfinder on careers). Benchmark C Utilize the Internet for research, classroom assignments and appropriate personal interests. Indicator 2 Create a product on a specific curricular topic that includes annotated Web sites constructed according to a standard style manual (e.g., electronic pathfinder on careers). Students may borrow career books and electronics books from the library to explore careers in the field and different applications in electronics. The school library media specialist may assist students in accessing the Ohio Career Information System Web site or other internet and print resources to find information on electricity careers and training opportunities. Research Connections: Marzano, R. et al. Classroom Instruction that Works: Research-based Strategies for Increasing Student Achievement. Alexandria, VA: Association for Supervision and Curriculum Development, 2001. 1. Nonlinguistic representations help students think about and recall knowledge. This includes the following: • Creating graphic representations (organizers), • Making physical models, • Generating mental pictures • Drawing pictures and pictographs, and 7

Series and Parallel Electric Circuits - Grade 11 • Engaging in kinesthetic activity 2. Cooperative learning has a powerful effect on student learning. This type of grouping includes the following elements: • Positive interdependence, • Face-to-face promotive interaction, • Individual and group accountability, • Interpersonal and small group skills, and • Group processing 3. Generating and testing hypotheses engages students in one of the most powerful and analytic of cognitive operations. It deepens students’ knowledge and understanding. Any of the following structured tasks can guide students through this process: • Systems analysis, • Problem solving, • Historical investigation, • Invention, • Experimental inquiry, • Decision making Daniels, H., and Bizar, M. Methods that Matter: Six Structures for Best Practice Classrooms, Portland, ME: Stenhouse Publishers, 1998. Authentic experiences help students develop real-world knowledge and skills and apply their learning in ways that prepare them for their careers and lives beyond school. Edelson, D., Gordin, D., Pea, R. (1999). Addressing the Challenges of Inquiry-Based Learning, Technology and Curriculum Design. Journal of the Learning Sciences, 8(3-4), 391-450. Inquiry-based learning helps students to become resourceful, effective investigators and problem-solvers. Research reports that with effective teacher facilitation, studentcentered inquiry projects can reverse patterns of underachievement. Inquiry-based projects can build learning communities that foster communication skills, interpretive abilities and an understanding of issues from a variety of perspectives. Technology for All Americans Project, Measuring Progress: A Guide to Assessing Students for Technological Literacy, Reston, VA: International Technology Education Association, 2004. Standards-based student assessment supports the systematic, multi-step process of collecting evidence on student learning, understanding and abilities and using that information to inform instruction and provide feedback to the learner, thereby enhancing learning. Students should be assessed often using a variety of tools and methods. The design of student assessments should follow set principles, such as utilizing authentic

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Series and Parallel Electric Circuits - Grade 11 assessment that provides students the opportunity to demonstrate their knowledge and abilities in real-world situations. Note: the complete publication and other resource materials are available online at the Ohio page of the ITEA Center to Advance the Teaching of Technology and Science [CATTS] web link: http://www.iteaconnect.org/EbD/CATTSresources/CATTSresourcesOH01.htm General Tips: • Build circuits and then relate them to the laws that govern electron flow to make learning electronics fun. Some students learn in this manner better than doing the computations first. • Remember to emphasize that students need to switch leads and settings when measuring current. The multi-meter fuse can burn if this is not operated correctly. Emphasize that voltage is measured across a resistor while current is measured within the path. • Try out experiments before demonstrating them to students. • Collect as many electronic gadgets as possible for students to disassemble and learn from circuits therein. Teams of two work well. • Provide the lab procedure a class earlier so that students know what activities they will perform, hence saving time from reading instructions in class. • While students build their circuits, move from team to team, encourage and assist them as necessary. Try not to give answers while they experiment. • Instruct students on safety issues related to electronic circuits and general lab safety prior to each experimental exercise. Attachments: Attachment A, Pre-Assessment Attachment B, Pre-Assessment Answer Key Attachment C, Resistor Value Table Attachment D, Exercises A, B & C Attachment E, Post-Assessment Guide – Sample Answers Attachment F, Post-Assessment Rubric for Grading Attachment G, Series Circuit Analysis – Demonstrations Attachment H, Parallel Circuit Analysis – Demonstrations Attachment I, Post-Assessment Attachment J, Series Circuit Assignment and Recording Sheet Attachment K, Parallel Circuit Assignment and Recording Sheet

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Series and Parallel Electric Circuits - Grade 11 Attachment A Pre-Assessment Name_________________________ •

Define electrons, current, voltage, resistance, load, Ohm's Law, open circuit, and closed circuit. o Electrons – o Current – o Voltage – o Resistance – o Load – o Ohm's Law – o Open circuit – o Closed circuit –

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Sketch a closed series circuit. Label a DC voltage source, a load (two resistors) and a path.

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Sketch a closed parallel circuit. Label a DC voltage source, load (2 resistors) and the branches.

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List one example of where each of these circuits may be used.

Series – Parallel – 10

Series and Parallel Electric Circuits - Grade 11 Attachment B Pre-Assessment Answer Key •

Define electrons, current, voltage, resistance, load, Ohm's Law, open circuit, and closed circuit. o Electrons – negative charge of atoms o Current – flow or movement of electrons o Voltage – electromotive force o Resistance – opposition to flow or movement of electrons o Load – electronic component that consumes electrons o Ohm's Law – voltage equals current multiplied by resistance o Open circuit – circuit path with a break in it o Closed circuit – circuit path that has continuity

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Sketch a closed series circuit. Label a DC voltage source, a load (two resistors) and a path.

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Sketch a closed parallel circuit. Label a DC voltage source, load (2 resistors) and the branches.

•

List one example of where each of these circuits may be used.

Series – e.g., batteries in a flashlight; audio speakers in series to increase load impedance Parallel – e.g., streetlights; audio speakers in parallel to increase acoustical output

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Series and Parallel Electric Circuits - Grade 11 Attachment C Resistor Value Table Ohms in resistors and tolerances Color Black Brown Red Orange Yellow Green Blue Violet Gray White Gold Silver No band

Numerical value of first and second bands 0 1 2 3 4 5 6 7 8 9

Multiplying factor third band 1=100 10=101 100=102 1000=103 10,000=104 100,000=105 1,000,000=106 10,000,000=107 100,000,000=108 1,000,000,000=109 .1=10-1 .01=10-2

Percent tolerance fourth band

5% 10% 20%

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Series and Parallel Electric Circuits - Grade 11 Attachment D Exercises A, B & C Exercise A Select the resistors as labeled and record their respective tolerances. Calculate the value of each of the six resistors and record the resistance value in the appropriate space. Using a multi-meter, measure each resistor and record its value in the appropriate space. Calculate the difference and provide a reason for it. Resistor

Tolerance

Measured Value

Calculated Value

Difference

Reason for Difference

A B C D E F

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Series and Parallel Electric Circuits - Grade 11 Attachment D Exercises A, B & C (continued) Exercise B Using a multi-meter, measure and record the voltage values of batteries. Battery

Rated Value

Measured Value

Difference

Reason for difference

A B C D

Exercise C 1. Place batteries A, B, C, and D in a series circuit and measure total voltage value: ___________________ 2. Place batteries A, B, C, and D in a parallel circuit and measure total voltage value: ___________________ 3. Record the difference of Question 1 (series) from Question 2 (parallel) above: ____________________ 4. Explain the difference in voltage value as recorded in Question 3 above: _________________________________________________________________________ _________________________________________________________________________

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Series and Parallel Electric Circuits - Grade 11 Attachment E Series Circuit Analysis - Demonstrations •

Sketch a series circuit on the board, and place values for voltage and resistors. The example given below has a 12 VDC voltage value and two 2 kΩ resistors. Perform a calculation on the board to find current. Series circuit: use 2 x (2kΩ), 12V; I=12V/4kΩ = .003A or 3mA Then use different resistors (2kΩ and 3kΩ) to show the decrease in current when resistors value increases I=12V/5KΩ = .0024A or 2.4mA.

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Calculate the Voltage drop across each resistor. Voltage drop of each resistor is 2.4 mA X 2KΩ = 4.8V and 2.4 mA X 3KΩ = 7.2 V

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Apply Kirchoff's Voltage Law, and show 4.8 V + 7.2 V = 12 V = original voltage source.

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Demonstrate how to build the circuit on the breadboard translating the schematic to the breadboard. Measure the current in the path, and then measure the voltage drops across each resistor. Record your observations on the recording sheet.

Students solve the following problem: Given: One 12 V DC power supply and two 2 kΩ resistors. a. Calculate the current through the circuit. b. Build a series circuit on the breadboard and measure its current. c. Are the results between A and B different? If yes, why? If no, why not?

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Series and Parallel Electric Circuits - Grade 11 Attachment F Series Circuit Assignment and Recording Sheet Given: One 12 V DC power supply and two 2 kΩ resistors. a. Calculate the current through the circuit. b. Build a series circuit on the breadboard and measure its current. c. Are the results between A and B different? Why or why not? Calculated

Measured

Difference

Reason

Total Voltage VR1 VR2 Current Resistance Note: VR1 is voltage across resistor 1, and VR2 is voltage across resistor 2.

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Series and Parallel Electric Circuits - Grade 11 Appendix G Parallel Circuit Analysis - Demonstrations •

Sketch a parallel circuit on the board and place values for voltage and resistors. The example given below has a 12 VDC voltage value and two 2 kΩ resistors. Perform a calculation on the board to find total current and current through each branch. Circuit 2: Parallel circuits use two similar resistors (2kΩ). 1/RT = 1/R1 + 1/R2 = 1/2kΩ + 1/2kΩ = 1; RT = 1/1= 1kΩ IT= 12V/1kΩ = 12mA I1= 12V/2KΩ = 6mA; I2 is the same.

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Point out that the current in the parallel circuit is higher than the series circuit. Ask the question why this is so? Then show how the current in each branch uses different resistors. 1/RT = 1/R1 + 1/R2 = 1/2kΩ+1/3kΩ = 0.833; RT = 1/0.83= 1.2KΩ IT = 12V/1.2KΩ = 10 mA I1 = 12V/2KΩ = 6mA I2 = 12V/3KΩ = 4mA

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Point out that total resistance is less than the lowest resistor value in the branch. Also, voltage in each branch is equal to the source voltage.

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Apply Kirchoff's Current Law, and show 6mA + 6mA = total current for the circuit with two 2 kΩ resistor or 6mA + 4mA = 10 mA which is the total current for the circuit with a 2kΩ and a 3 kΩ resistor.

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Demonstrate how to build a parallel circuit on the breadboard, translating the schematic to the breadboard. Measure the current in the branches, and then measure the voltage drops across each resistor. Record your observation on the recording sheet.

Students solve the following problem: Given: One 12 V DC power supply and two 2 kΩ resistors. a. Calculate the current through each branch of the circuit. b. Build a parallel circuit on the breadboard and measure its current. c. Are the results between A and B different? If yes, why? If no, why not?

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Series and Parallel Electric Circuits - Grade 11 Attachment H Parallel Circuit Assignment and Recording Sheet Given: One 12 V DC power supply and two 2 kΩ resistors. a. Calculate the current through the circuit (through each branch and total current). b. Build a parallel circuit on the breadboard and measure its current. c. Are the results between A and B different? If yes, why? If no, why not? Calculated Total Voltage Total Current Current

Measured

Difference

Reason

IR1 IR2

Total Resistance Note: IR1 is current through resistor 1, and IR2 is current through resistor 2. One resistor can be replaced by a 3 kΩ resistor to show the difference in current. Use the current divider rule to compute for current in a desired branch: Current divider formula: Ix = (RT/Rx )*IT

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Series and Parallel Electric Circuits - Grade 11 Attachment I Post-Assessment Name________________________ Directions: In teams of two, complete the following to the best of your ability. Discuss your responses with your teammate before writing them on the provided answer sheet. 1. Series Circuits: a. List one application where a series circuit would be the best choice ___________________. b.

Describe why a series circuit would be the best choice (include at least two reasons).

2. Parallel Circuits: a. List one application where a parallel circuit would be the best choice ____________________. b.

Describe when the parallel circuit would be the best choice (include at least two reasons).

3. Given: one 12 V DC power supply and two speakers rated as 4KΩ (speaker A) and 8KΩ (speaker B). a. Determine how the speakers would be connected to achieve the greatest sound (Assume that the greater the current flow, the greater the sound.) Series: RT, IT. Parallel: RT, IT . b.

Sketch your schematic circuit.

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Series and Parallel Electric Circuits - Grade 11 Attachment I Post-Assessment (continued) c.

Build your circuit on the breadboard and measure all voltage drops and currents. Measurements are taken at definite points. For voltage, a point means “across a resistor,” while for current, a point means “current flowing into the resistor.” Record the values in the table below or as instructed:

Sample Table: Point

Calculated Measured Voltage Voltage

Voltage Variance

Calculated Current

Measured Current

Current Variance

1 2 3 4 d.

Compare your measured values to your calculated values.

e.

If the speakers are to be installed in a car, which speaker would be placed next to the driver’s seat, and which would be placed farther away?

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Series and Parallel Electric Circuits - Grade 11 Attachment J Post-Assessment Guide – Sample Answers Directions: In teams of two, complete the following to the best of your ability. Discuss your responses with your teammate before writing them on the provided answer sheet. 1. Series Circuits: a. List one application where a series circuit would be the best choice. Battery example: Battery arrangement to maximize voltage – two 12 VDC batteries connected to power a 24 VDC diesel engine. Wiring example:

b. Describe why a series circuit would be the best choice (include at least two reasons). Example (benefits): I. maximizing resistance (load), such as in space heaters. II. minimizing current, such as reduction of current to electronic components. 2. Parallel Circuits: a. List one application where a parallel circuit would be the best choice. Cafeteria Example: Lights in a cafeteria

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Series and Parallel Electric Circuits - Grade 11 Attachment J Post-Assessment Guide – Sample Answers (continued) Wiring Example:

b. Describe when the parallel circuit would be the best choice (include at least two reasons). Example (benefits): I. equal voltage, from one power supply, is required for various branches of a system, such as cafeteria lighting, streetlights, and 110V outlets in houses. II. failure in one load should not fail the rest of the system, if one street light goes out, the rest should stay on. 3. Given: one 12 V DC power supply and two speakers rated as 4KΩ (speaker A) and 8KΩ (speaker B). a. Determine how the speakers would be connected to achieve the greatest sound. (Assume that the greater the current flow the greater the sound.) Series: RT = 4 kΩ + 8 kΩ = 12kΩ; IT = V/ RT = 12V/12kΩ = 1mA. Parallel: RT = [(4*8)/4+8] kΩ = 2.66kΩ; IT = V/ RT = 12V/2.66 kΩ = 4.51mA. b. Sketch your schematic circuit. Parallel circuit c. Build your circuit on the breadboard, and measure all voltage drops and currents. Measurements are taken at definite points. For voltage, a point means "across a resistor," while for current, a point means "current flowing into the resistor." Record the values in the table below or as instructed:

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Series and Parallel Electric Circuits - Grade 11 Attachment J Post-Assessment Guide – Sample Answers (continued) . Sample Table: Point

Calculated Measured Voltage Voltage

Voltage Variance

Calculated Current

Measured Current

Current Variance

1 2 3 4 d. Compare your measured values to your calculated values. Answers should not vary much. Reasons for variation may include: instrument error, human error, circuit component value accuracy. e. If the speakers are to be installed in a car, which speaker would be placed next to the driver’s seat, and which would be placed further away? Why? •

The greater the current the louder the sound. Using the current divider formula [Ix = (RT/Rx )*IT ], the current going through the 4Kohm resistor would result in a 2.999mA, while the 8Kohm will pass 1.5mA.

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Therefore, the speaker rated at 4Kohm will produce the loudest sound and can be placed further away while the higher rated speaker (8kohm) can be placed next to the drivers seat.

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Series and Parallel Electric Circuits - Grade 11 Attachment K Post-Assessment Rubric for Grading Characteristic or Attribute

Exemplary 4

Accomplished 3

Developing 2

Beginning 1

Depth of understanding

Technological responses are accurate and thoughtfully explained.

Technological responses are accurate.

Technological responses have occasional inaccuracies or are simplified.

Technological responses have major inaccuracies and are overly simplified.

Data collection and communication

Technological information and data collection are communicated clearly and precisely. An element of innovation may be included.

Technological information is communicated clearly.

Technological information has some clarity.

Technological information is unclear.

Application

Presents a clear design of an electric circuit to achieve the greatest sound. The circuit is built correctly and all appropriate measurements are measured and calculated correctly.

Presents a design of an electric circuit. The circuit is built correctly and some measurements are measured and calculated correctly.

Presents a design of an electric circuit. The circuit is built correctly. The measured measurements are correct but calculated measurements are incorrect (or viceversa).

Presents a design of an electric circuit. The circuit is built correctly. Measurements are incorrect or missing.

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