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# Current And Voltages

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### Current And Voltages

1. 1. Introduction to Electronics Unit One: DC Circuits Section Three Current and Voltage
2. 2. Current, Voltage and Power <ul><li> Students will be able to: </li></ul><ul><li>Explain that energy is transformed, not created. </li></ul><ul><li>State types of energy. </li></ul><ul><li>Define </li></ul><ul><ul><li>Electron </li></ul></ul><ul><ul><li>Current </li></ul></ul><ul><ul><li>Voltage </li></ul></ul><ul><ul><li>Power </li></ul></ul><ul><li>Examine the relationship between current, voltage and power. </li></ul><ul><li>Name the symbol for current, voltage and power. </li></ul><ul><li>Tell the unit and unit symbol for current, voltage and power. </li></ul><ul><li>Calculate missing elements using the ampere formula. </li></ul><ul><li>Calculate missing elements using the power formula. </li></ul><ul><li>Predict the effect of connecting batteries in series or parallel form. </li></ul>
3. 3. Current <ul><li>Current is the flow of electrons within an electrical circuit. </li></ul><ul><li>The word current is represented in formulas using the letter I. </li></ul><ul><li>Current is measured in amperes (amps). </li></ul><ul><li>Amps are represented in formulas using the letter A. </li></ul><ul><li>Current moves away from a negative charge and towards a positive charge. </li></ul>
4. 4. What is an Ampere? <ul><li>Ampere (A) represents the amount of electrons that flow past a point in a circuit in one second. </li></ul><ul><li>Formula: I = Q/t </li></ul><ul><li>The word coulomb is represented in formulas using the letter Q. </li></ul><ul><li>6,280,000,000,000,000,000 electrons equals one coulomb (C). </li></ul><ul><li>One coulomb moving past a point in one second equals one ampere. </li></ul><ul><li>Time is represented by t, and using the units of seconds (s). </li></ul>
5. 5. Calculating Amperes (I) <ul><li>Calculate the current moving past a point in a circuit if 24 coulombs travel past it in 6 seconds. </li></ul><ul><li>How long would it take 30 coulombs to travel past a point if the circuit had a current of 5 amps? </li></ul><ul><li>How many coulombs would travel past a point in 5 seconds if the circuit had a current of 7 amps? </li></ul>
6. 6. Answers to Ampere Questions Q = 35C t = 6s I = 4A Q = 7A(5s) t = 30C / 5A I = 24C / 6s Q = It t = Q/I I = Q/t I = 7A Q = ? t = 5s I = 5A Q = 30C t = ? I = ? Q = 24C t = 6s
7. 7. Voltage <ul><li>Voltage is a force that moves the electrons in a circuit. </li></ul><ul><li>The word voltage is represented in formulas using the letter E. </li></ul><ul><li>Voltage is measured in volts. </li></ul><ul><li>Volts are represented in formulas using the letter V. </li></ul>
8. 8. Energy Types <ul><li>Voltage is a method of producing electrical energy from another energy type. </li></ul><ul><li>Types of energy: </li></ul><ul><li>- Friction - Light </li></ul><ul><li>- Magnetism - Heat </li></ul><ul><li>- Chemical - Pressure </li></ul>
9. 9. Increasing Voltage Using Cells & Batteries <ul><li>When batteries are connected in a series format the voltage in the circuit is increased. </li></ul><ul><li>The current in the circuit will pass through all the batteries as they are connected in series. </li></ul><ul><li>By connecting the batteries in series form you increase the total voltage. A higher voltage means the component/ device will have a stronger output. Ex. A light would be brighter. </li></ul><ul><li>I T = I 1 = I 2 = I 3 </li></ul><ul><li>E T = E 1 + E 2 + E 3 </li></ul>
10. 10. Increasing Current using Cells & Batteries <ul><li>When batteries are connected in a parallel format the current in the circuit is increased. </li></ul><ul><li>The total voltage in the circuit remains the same. </li></ul><ul><li>By connecting the batteries in parallel form you increase the length of time the circuit will function. The circuit will use the power one at a time rather than as a combined force. </li></ul><ul><li>I T = I 1 + I 2 + I 3 </li></ul><ul><li>E T = E 1 = E 2 = E 3 </li></ul>
11. 11. Calculations <ul><li>For each of the circuits below calculate the total voltage. </li></ul><ul><li>Each battery is 1.5 V. </li></ul>E T = E 1 = E 2 = E 3 E T = 1.5 V = 1.5 V = 1.5 V E T = 1.5 V E T = E 1 + E 2 + E 3 E T = 1.5 V + 1.5 V + 1.5 V E T = 4.5 V
12. 12. Increasing Current and Voltage <ul><li>To get both an increase in the current and the voltage, cells or batteries would have to be connected in both series and parallel format. </li></ul>
13. 13. Power Power is the amount of energy used when a circuit is complete, in operation. Power can be calculated for time periods: watts per seconds or watts per hour. The word power is represented in formulas using the letter P. Power is measured in watts. Components in a circuit either consume, transfer, store, or transform power to another energy form. - Resistive components consume power. - Conductors transfer power. - Cells and capacitors store power. - Speakers, LEDs, and motors transform power.
14. 14. Calculating Power <ul><li>Power consumption can be calculated for an entire circuit or at each component in a circuit. </li></ul><ul><li>Formula: P = IE </li></ul><ul><li>What is the total power consumption for the circuit below? </li></ul><ul><li>Diagram: 9V, 3A </li></ul><ul><li>Determine the voltage if a circuit has 75 watts of power and a current of 15 amps. </li></ul><ul><li>What is the required current for a 60 watts, 20 volt electrical device? </li></ul>
15. 15. Answers to Power Questions I = 3A E = 5V P = 27 watts I = 60 watts / 20V E = 75 watts / 15A P = 3A(9V) I = P/E E = P/I P = IE P = 60 watts I = ? E = 20V P = 75 watts I = 15A E = ? P = ? I = 3A E = 9V
16. 16. Assignments <ul><li>KSB : Current, Voltage and Power </li></ul><ul><li>Textbook Reading and Questions: </li></ul><ul><li>Read chapters 2,3,7, (pages 9-29, 70-71). </li></ul><ul><li>Questions listed in KSB Activity Directions. </li></ul><ul><li>Journal Activity : </li></ul><ul><li>Electronics Web Site Reference Chart – One web site that deals with current, voltage and power. </li></ul>Click on home section. Content for all levels. Little bit of everything DC circuits. Excellent. All Grades http://www.ndt-ed.org/EducationResources/HighSchool/Electricity/hs_elec_index.htm Content Grades Web Site
17. 17. Image Bibliography <ul><li>Slide 3: </li></ul><ul><li>www.discover.edventures.com </li></ul><ul><li>Slide 4: </li></ul><ul><li>www.why files .larc.nasa.gov/text/kids/Problem_Board/problems/electricity/ circuits 2.html </li></ul><ul><li>Slide 7: </li></ul><ul><li>www.SolarSam.com </li></ul><ul><li>Slide 8: </li></ul><ul><li>http://www.sln.org/guide/hughes/10types/typesmagnetic.html </li></ul><ul><li>http://www.sln.org/guide/hughes/10types/typeslight.html </li></ul><ul><li>Slide 9: </li></ul><ul><li>www.iss.cet.edu </li></ul><ul><li>Slide 10: </li></ul><ul><li>www.pzweb.harvard.edu </li></ul><ul><li>Slide 11: </li></ul><ul><li>Created using PCB123 Schematic Version 2.1.0.600 </li></ul><ul><li>Slide 12: </li></ul><ul><li>Created using PCB123 Schematic Version 2.1.0.600 </li></ul><ul><li>Slide 13: </li></ul><ul><li>http:// www.gifanimations.com/action/ImageDisplay?group =1&category=23&index=48&dir=stay </li></ul>