Physics Regular 1617 Williams. Electric Current & Circuits

Transcription

1 Physics Regular 1617 Williams Electric Current & Circuits 1

2 2

3 Drawing Schematics Not everyone is a great artist and everyone draws a little bit differently. To make it easier for everyone to understand how a circuit is supposed to be assembled, standard symbols for circuit components are used. Circuit "drawings" using these common symbols are called schematic. There are a rich number of symbols we could use, but since this is an introduction and since we won't use that many components, we only have to learn the ones below. Please follow along and draw them. They will serve as a nice reference. Single battery (or general voltage source) Double battery (two batteries in series; series means one follows right after the other) Resistor (a general, nonspecific, symbol) Light bulb (a specific kind of resistor) Wire (conducting wire) Ammeter (always draw series) Ohmmeter (always draw in parallel) Voltmeter (always draw in parallel) Drawing whole circuits (multiple symbols) 1. Draw a schematic for a: Single battery with two light bulbs in series. 2. Draw a schematic for a: Single battery with three light bulbs in series. Measure the voltage across the first resistor. 3. Draw a schematic for a: Double battery powering pencil sharpener (show a general resistor). Also, measure the current flowing through the resistor. 4. Draw a schematic for a: Double battery powering a light bulb. Measure current through the bulb and voltage and resistance (ohms) across the bulb. 3

4 Day 1 Circuit Goals 1. Verify circuit a. Make sure you have seven wires b. Paper belongs under board at all times c. Show how a PCB board is made ("printed" wires connect various spots) d. Show how springs connect wires e. Demonstrate how to NOT twist a resistor f. Multimeter i. Pick same number for your table each time and make sure turned off (doesn't turn off automatically, battery will die quickly) ii. Show three regions and prefixes (show AC we don't use) iii. Show black com port and red port (10A and VΩ) iv. Measure each battery at 1.5V, replace if under about 1.1 V v. Connect battery in series and show why adds voltage vi. Show 1 dot is not a reading (off scale) vii. Show continuity tester viii. Discuss why 10A is very low resistance and VΩ is very high resistance ix. Check continuity of each bulb, replace with other circuit if possible x. Add post-it note to your board, same number as your resistor xi. Measure cold resistance of bulb filament (MUCH higher when lit why?) xii. Show a battery using ammeter to find current (BRIEFLY, or drains battery quickly) xiii. Pass out weekend HW & work on (mandatory unless told otherwise ask teacher) 2. Use ammeter 3. Use ohmmeter 4. Create parallel and series circuits and understand: a. Series circuits have same current, but share voltage b. Parallel circuits have same voltage, but share current Day 2 Circuit Goals 1. Make wires a. Demonstrate, have one person from each row make a wire and everyone strip off one wire tip.later b. Note how this will be useful for Robot Project 2. Use ammeter a. Set up multimeter as ammeter b. Set up a circuit with a: single light bulb and 3 V EMF. i. Find the cold resistance of the bulb ii. Draw schematic and equipment diagram (use tablet to show). iii. Replace wire with ammeter. Measure current and voltage drop across bulb. iv. Compute power of bulb v. Compute the hot resistance of the bulb. How do they compare and why? (hint: bulb is HOT) vi. REMEMBER: To measure the current flowing through a wire, replace the wire with an ammeter.ammeters are always placed in series, NEVER in parallel Circuit Goals - Day 3 1. Two of same resistor in series and in parallel - do circuit and schematic diagrams for ALL a. Check resistance with ohmmeter for both b. Connect to two batteries in series (double battery) and check voltage drop in series and parallel c. Put resistor in series and in parallel with bulb...any difference in brightness? Why? 4

5 Physics Circuit Project: Answering Robot Challenge for each student pair: Build a robot that has the ability to indicate which answer is correct when given special multiple choice review question cards that you make. Robot Guidelines: 1. Robot must indicate the correct answer by doing something obvious such as a light turns on, a sound buzzes, some part moves, etc Robots must be homemade- no toys, kits, or pre-made robotics. 3. Individual parts such as lights, buzzers may be purchased but most of robot should come from common inexpensive household items. 4. Robot should be made so its internal workings/wires can be inspected by teacher. 5. Best robots will have strong connections (wire nuts/solder), long flexible wires, at least 2 strong signals (probably in parallel), look unique & fun Performance (10 pts) Appearance (10 pts) Ease of use (10 pts) Cards (10 pts) Doesn't work no features very difficult 1 card = 2 points Needs assistance some details needs assistance 2 cards = 4 points Weak/intermittent Neutral Adequate 3 cards = 6 points Strong signal Attractive Reliable 4 cards = 8 points Multiple signals Excellent Enjoyable 5 cards = 10 points Grade = 100% * Total Points / 40, the best ones in class will get A+ (10/10) for any particular category About the cards: Make 5 cards having a multiple choice question and at least 3 answers. The questions should be your own, & helpful for finals. The card is made of 2 index cards stapled together. The front card has the question with an answer hole, and holes for answers A, B, C, D, etc. The front of the inside card has a piece of aluminum foil for the question and answer holes, as well as a longer piece of foil connecting the question hole to the correct answer hole. Sample wiring At right shows how to wire the inside of a question card. The grayed blocks represent conductive metal foil cut-outs. The circuit patter at left is wired so the correct choice is A. Tips: Try to get two strong signals for performance. Usual signals include: sound, motion, lights. Appearance should impress people and it should be obvious effort went into the appearance. Ease of use will require long, reasonable flexible arms. A user should be able to test all possible answers with the card on the table and without having to bend the robot body forward. At least one card per deck will be checked by me; additionally, cards will be checked by your peers. Make good questions with the correct answer. If I spot a wrong answer or a bad question, I will check that deck more carefully. 5

6 Physics Circuit Robot: Judgment Day! Your name or student ID: The robot project will also have a theme of some kind. The theme should be clever and creative and it should be carried out consistently within the robot and the question cards. It is expected that you will use class time wisely in this project and come up with meaningful questions. On presentation day, I will ask you to visit the various projects and see how useful they are in helping you to study and also how impressed you are with the quality of the various project. I want you to do this judging with your partner in order to encourage a discussion about the strengths and weaknesses of the projects. Guidelines 1. Robot must indicate the correct answer by doing something obvious such as a light turns on, a sound buzzes, some part moves, etc Robots must be homemade- no toys, kits, or pre-made robotics. Individual parts such as lights, buzzers may be purchased but most of robot should come from common inexpensive household items. 3. Robot should be made so its internal workings/wires can be inspected 4. Best robots will have strong connections (wire nuts/solder), long flexible 5. Wires, at least 2 strong signals (probably in parallel), look unique & fun Rubric Performance Appearance Ease of use Cards Doesn t work No features Difficult to use even with help Needs assistance Some details Needs assistance (hard to do by yourself) Weak or intermittent signal Neutral Can do by yourself, but challenging (short arms, etc.) Strong signal Attractive Reliable and reasonably easy to use Best in class/very impressive! Excellent Simple to use, so it s phun! 2 points per card up to 5 cards List in order the top 4 performing robots by categories. Please, don t include your own robot. Include name of at least one member of group. Place Performance Appearance Ease of use Cards Best in this category 2 nd best 3 rd best 4 th best All things considered. The best robot & 2 nd best robot overall were which ones and why do you think so? 6

7 7

8 8

9 9

10 10

11 11

12 12

13 13

14 14

15 Unit 06 Vocabulary and Equations Current Electricity & Circuits Vocabulary: previous vocabulary electric current, ampere, amp (A), Coulomb (C) electrical potential, voltage (V), electromotive force (emf) potential difference resistor, resistance (Ω), equivalent resistance, load power (W) Ohm's law, ohmic conventional current, drift velocity, drift speed cross sectional area circuit breaker, fuse, potentiometer direct current (DC), alternating current (AC) kilowatt-hour electric circuit, series circuit, parallel circuit resistors in series, resistors in parallel closed circuit, open circuit, short-circuit switch multimeter, COM port, conductivity tester wire, conductor, insulator circuit diagram, schematic, schematic symbols battery, positive terminal, negative terminal Symbols: V, ΔV, i, ΔQ, Δt, R, A, Ω, W, P Equations & constants: You get these on test: i = ΔQ/Δt ΔV = i R Equivalent resistance: Series R e = R 1 + R 2 Parallel 1/R e = 1/R 1 + 1/R 2 P = E/t P = iv P = V 2 /R Cost = rate x energy Resistor codes (use these, don t memorize them) Number Color Number Color 0 Black 5 Green 1 Brown 6 Blue 2 Red 7 Violet 3 Orange 8 Gray 4 Yellow 9 White NOT provided on test: 1 st digit/2 nd digit/# of zeros Unit Objectives - Williams 1. I understand all the vocabulary & math of this unit and all demos, videos, equations, and class assignments. 2. I remember objectives & vocabulary from previous units. 3. I know electrical potential (V), electrical potential energy, can distinguish them, and batteries provide energy for this 4. I understand conventional current, know current flow direction versus electron flow and know about drift speed 5. I know the difference between how quickly current starts to flow versus how fast electrons move 6. I understand resistance and how/why it's impacted by wire length, area and temperature 7. I know the wide variety of the human body's electrical resistance and its possible deadly consequences 8. I can contrast AC/DC and know North American AC's standards and common battery voltage standards 9. I know what an electrical panel, circuit breaker/fuse, and 120V/240 household voltages are and their dangers 10. I can use Ohm's law, equations of power, and equivalent resistance to solve problems 11. I understand and can compute circuit energy costs for local household rates 12. I know the function and operation of the multimeter and circuits we used and learned about in this class 13. I understand how a light bulb works including its entry and exit points for current 14. I know that it only makes sense to transport electrical energy over long distances using high voltages 15. I can draw/ recognize schematic symbols we use in class: emf (battery single/multiple), wire, resistor, switch 16. I can find R e for series, parallel and mixed circuits 17. I know computationally zero voltage drop occurs along wires and can solve complex circuit diagrams using R e 18. I understand the differences between light bulbs in series compared to light bulbs in parallel, including how brightly they shine, the power consumed, ΔV, and the consequence of losing one of those bulbs 19. I understand the consequences of additional resistors being added in parallel versus series 20. I can explain electrical analogies like how water/electricity/shopping lines are similar 21. When given a table with resistor stripe codes, I can use these codes to find the ohms of the resistor 22. I can use electrical test equipment and build circuits from both equipment and schematic diagrams (*from using) 23. I know where voltmeters, ammeters and ohmmeters go in circuits and understand why DuPage ROE Objectives 601. I can apply Ohm s Law I can recognize and analyze series and parallel circuits I can identify how to measure voltage and current with an appropriate meter I can calculate the power used by an electronic device. 15

16 06Current Electricity-Calendar Bold and underlined means put in journal notes Introduce circuits concepts with CCK (circuit construction kit, day 1) Electricity Introduction Notes (06-01) & drawing 1 Fr:11/04/16 schematics in packet H06-01 Get computers booting up Notes (06-02), parallel resistors and wire properties CCK day 2 with challenges (red/black leads, open and 2-LS Mo:11/07/16 closed circuit effects on dimness & complex challenges) H06-02 Notes (06-03), solving simple circuits. 3 Tu:11/08/16 CCK day 3 with challenges H06-03 Notes (06-04), circuit boards: care and use Circuit boards, pts: 15 pts: 5 pts participation (time spent wisely in class), 5 pts levels 1 & 2; 5 pts, last day quiz Circuit introduction, day 1, mastery level 1: meter settings & prove measurement of V and R 4 We:11/09/16 Introduce Moodle Q s H06-04 Circuit challenges, day 2: Notes (06-05), Resistor codes, equipment diags, bulb changes A few clix Some of packet day 2 goals; Peer helpers 5 Th:11/10/16 HW and Moodle time after checked H06-05 Day 3: Packet goals together A few clix Paper check (day 2) and first done become peer helpers Introduce Robot project & plan in groups 6 Fr:11/11/16 Any level 1 make ups? H06-06 Circuit challenges, day 4 (Level 2: Pairs: parallel and series bulbs including schematic and equipment diags) 7-LS Mo:11/14/16 HW/Moodle time H06-07 A few clix; Robot review, Circuit challenges, day 5, Last day for levels 1 and 2 Notes (06-06), fuses and electrical safety Moodle and HW time 8 Tu:11/15/16 Parent Participation H06-08 Study for electricity test A/B (individual) 5pt lab Quiz Moodle due day after 9 We:11/16/16 Circuit challenges, robot time, test review work test 10 Th:11/17/16 Electricity test Work on robot 11 Fr:11/18/16 Robot time, make-up tests, review HW Work on robot Finish up robot! 12 Mo:11/21/16 Robot time, Research due next Mo. 13 Tu:11/22/16 Robot project due! Pick out a turkey 14-ED We:11/23/16 Short day review activity with some points Eat yummy turkey Th:11/24/16 Fr:11/25/16 16