Download A Hands-On Approach to Ohm`s Law and DC Circuits

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A ConsuLab presentation
HAND’S ON APPROACH TO TEACHING
CIRCUIT ANALYSIS & OHM’S LAW
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AL SANTINI – JUNE 2014
[email protected]
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C I R C U I T A N A LY S I S & O H M ’ S L AW
A Hand’s On Approach to Teaching Circuit Analysis and Ohm’s Law By: Al Santini – ConsuLab, June 2014 Within this seminar we will look at a traditional method of teaching Ohm’s Law and circuit analysis, which involves white board drawing and some math for understanding. We will look at the potential problems with this method especially with the student of today. We will then use a modern trainer to build and analyze basic circuits and prove that ohm’s law actually works. Problems with the traditional method: 1.
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Students today are used to “live” information at their finger tips Math may not be the strong point of many students Just about anyone learns better if they can hold, touch or experience the concepts If a picture is worth a thousand words, then hand’s on is worth a million pictures Using a white board to: 1.
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Draw a picture of a circuit Add in resistance values, voltages, and current Calculating a value Do it for series, parallel and series parallel circuits 5. Add unwanted resistance to cause voltage drops in various parts of the circuit 6. Use math to prove all parts of circuit Is this really the best way to get across this extremely important concept? 1. Is math a strong point of many students 2. Is math a strong point of instructors 3. For example, the student needs to know that the total resistance of a parallel circuit is always lower than the lowest resistance. The parallel resistance formula consulab.com
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Perhaps a better method might be met with better success: 1.
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Discuss Volts as pressure (maybe use pressure in a tire as an example) Discuss Current as quantity (the air in the tire) Discuss resistance as the opposition to current flow (the rubber of the tire) Use the trainer to build a basic circuit Let’s look at the trainer and the workbook 1.
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Begins with a simple explanation Hand’s on assignment Fill in the blank assignment based on real measurements A test to show comprehension Wire a series circuit 1. Student does the hand’s on part so he/she is involved 2. Instant success as bulb lights 3. Measures voltage and current 4. Allows for a discussion of voltage drop occurring when current flows through resistance Add “unwanted” resistance 1. The student wires in some resistance 2. The resistance does no work that the student can see (no light) 3. Current flowing through resistance produces light, heat or magnetic field consulab.com
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4. Voltage drop reduces the productive work of the load (the light) 5. The light is dimmer 6. It does not matter where the resistance is places in this series circuit, the result is the same – reduced current flow and voltage drop 7. Allows for a discussion of “work” as wattage Wire a parallel circuit by using two equal size bulbs 1. Students can see the additional work being accomplished 2. Instructor can see that the circuit is correct by scanning the trainers 3. Switch back to same bulbs in series to see the brightness chance 4. Continue the discussion of wattage 5. Measure NOT talk about voltages and current flow 6. Calculate resistance off of applied voltage and current flow Add a 3rd bulb in parallel 1. “See” different resistance bulbs all working to full potential 2. Calculate total circuit resistance 3. Measure current flow of each bulb and calculate resistance (use my script calculator) consulab.com
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4. Active demo of resistance of parallel circuit lower than lowest individual resistance Add unwanted resistance to circuit 1. What impact on circuit performance does it have when it is in series 2. What impact on circuit performance does it have when it is in parallel 3. Students begin seeing effect of unwanted resistance causing voltage drop Electronics 1. Potentiometer 2. Diode 3. Transistor a. NPN b. PNP 4. Relay 5. Pulse width modulation (PWM) consulab.com
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TP (throttle position sensor) as an example of a potentiometer Diode 1. Composed of both positive and negative material that makes it polarity sensitive 2. When polarity is correct it will conduct 3. When polarity is not correct it will block 4. First use in alternators 5. Now hundreds in use on modern vehicle Two diodes together become a transistor 1. Base is the controller 2. Emitter and collector become part of the load circuit 3. NPN generally used to control the ground side of a circuit 4. PNP generally used to control the positive side of a circuit 5. Load is generally wired off of the collector consulab.com
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6. Transistors are sometimes compared to a water faucet 7. Relays and Flashers consulab.com
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Duty cycle – pulse width modulation 1.
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Duty cycle is measured as a percent
Results in longer or shorter on time for a component
Vertical lines signify transition between on and off
Many components are Pulse Width Modulated
Why teach circuits and ohm’s law hand’s on? 1.
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Makes ohm’s law fun
Makes teaching active
Allows instructor instant visual verification that circuit is wired correctly
Allows students to “see and experience” concepts involving circuits and indirectly
ohm’s law
5. Very limited math required
6. Very high degree of understanding
The hope is that you will try this method and experience great success with it. The ConsuLab trainer will allow you to teach an entire basic automotive electricity class hand’s on, beginning with meter reading, going through Ohm’s law with circuit building, control circuits and electronics. The trainer comes with a manual that can be followed individually by a student or a class. The trainer has common components and utilizes its own source of regulated power. The trainer and the meter are protected by commonly available fuses and/or circuit breakers. Thanks for attending…. Al Santini [email protected] consulab.com
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