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Physics 110

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  1. Physics 110 Fundamentals of Electronics

  2. Fundamentals of Electronics • Student Information Sheet • Syllabus • Blackboard • Books

  3. Physics 110 Lab • Labs start on Monday, September 12 • I have all labs posted in the calendar

  4. What Can I Expect? • Lecture Style • PowerPoint, Chalkboard, Demos • Class participation is good. • Exams • Exams problems are much like the homework problems and in-class exercises.

  5. Where do we find electrical circuits? • Communications • Radio, internet, telephone, television • Data Processing • Desktop computers, servers • Automobiles • displays, sensors, motors • Home • lighting, heating, appliances • Weather Stations • wind speed, precipitation, temperature • Power Plants • moving magnets, transformers

  6. Chapter 2 DC Networks

  7. Review Topics • Scientific Notation • Units of Measure

  8. Scientific Notation and Prefixes 1012 – tera (T) 109 – giga (G) 106 – mega (M) 103 – kilo (k) 100 10-3 – milli (m) 10-6 – micro (m) 10-9 – nano (n) 10-12 – pico (p) • 1,000,000,000,000 • 1,000,000,000 • 1,000,000 • 1,000 • 1 • 0.001 • 0.000001 • 0.000000001 • 0.000000000001 Write each number in scientific notation and give the metric prefix for each.

  9. Electrical Units SI

  10. Questions • What is the difference between AC, DC, and static electricity? • Why does a Van de Graaff Generator make your hair stand up? (Give a technical answer.) • Why do clothes sometimes stick together after you take them out of the dryer?

  11. What is Electricity? • From the Greek word “elektron” that means “amber” • There are two types of electricity: • Static Electricity - no motion of free charges • Current Electricity - motion of free charges • Direct Current (DC) • Alternating Current (AC)

  12. 2.2 Current • Current is the rate of flow of charge through a conductor. • Conductor • materials with free electrons • e.g. copper, aluminum, gold, most metals • Insulator • materials with no free electrons • e.g. glass, plastics, ceramics, wood • Semiconductor • a class of materials whose electron conductivity is between that of a conductor and insulator • Examples: Silicon, Germanium

  13. Can Air be a Conductor? • Yep!

  14. Electrical Current • Current - the rate of flow of charge through a conductor • Conventional Current • Direction of flow of positive (+) charges • Electron Current • Opposite to that of conventional current

  15. Equation for Current I=Q/t I = the current in Amperes (A) Q = the amount of charge in Coulombs (C) t = the time measured in seconds (s) • The charge of an electron is 1.6 x 10-19 C

  16. Effect of Electric Currents on the Body • 0.001 A can be felt • 0.005 A is painful • 0.010 A causes involuntary muscle contractions • 0.015 A causes loss of muscle control • 0.070 A can be fatal if the current last for more than 1 second

  17. Example Problem 2.0 • How much charge will pass through a conductor in 0.1 seconds if the current is 0.5 Amperes? • How many electrons are required for this much charge?

  18. Example 2.0 • T = 0.1 s I = 0.5 A I = Q/t, so Q = I*t = (0.5 A)*(0.1 s) = 0.05 C • Charge/e- = 1.6 X 10-19 C/e- # Charges = 0.05 C/ 1.6 X 10-19 C/e- # Charges = 3.125 X 1017 e-

  19. Example 2.1 • Determine the current in amperes through a wire if 18.726 x 1018 electrons pass through the conductor in 0.02 minutes. • 18.726 x 1018 electrons, t = 0.02 min Q = (18.726 x 1018 e-)(1.6 X 10-19 C/e-) Q = 2.99616 C  3 C • I = Q/t = 3 C/(0.02 min)(60 s/min) • I = 2.4968  2.5 A

  20. Example 2.2 • How long will it take 120 C of charge to pass through a conductor if the current is 2 A? • I = Q/t, so t = Q/I = 120 C/2 A t = 60 s

  21. Example Problem 2.3 and 2.4 • Write the following in the most convenient form using Table 2.1: (a) 10,000 V (b) 0.00001 A (c) 0.004 seconds (d) 520,000 Watts (e) 0.0006 A • 4200 V • 1,200,000 V • 0.00004 A (a) 104 V (b) 10-5 A (c) 4 X 10-3 s (d) 5.2 X 105 W (e) 0.6 mA (f) 4.2 kV (g) 1.2 MV (h) 40 mA

  22. Wire Gauge? • AWG = American Wire Gauge • AWG numbers indicate the size of the wire….but in reverse. • For example, No. 12 gauge wire has a larger diameter than a No. 14 gauge wire. • What do we use to keep wires from melting? • Answers: Fuses, Circuit Breakers, GFCI

  23. Fuses

  24. Circuit Breakers

  25. GFCI = Ground Fault Current Interrupter • Used in kitchens and bathrooms • Trip quicker than circuit breakers

  26. 2.3 Voltage • Voltage is the measure of the potential to move electrons. • Sources of Voltage • Batteries (DC) • Wall Outlets (AC) • The term ground refers to a zero voltage or earth potential.

  27. V A Digital Multimeters (DMM) Measurement Device Circuit Symbol Voltage Voltmeter Current Ammeter Resistance Ohmmeter

  28. Batteries • A battery is a type of voltage source that converts chemical energy into electrical energy • The way cells are connected, and the type of cells, determines the voltage and capacity of a battery

  29. More on Batteries • Positive (+) and Negative (-) terminals • Batteries use a chemical reaction to create voltage. • Construction: Two different metals and Acid • e.g. Copper, Zinc, and Citrus Acid • e.g. Lead, Lead Oxide, Sulfuric Acid • e.g. Nickel, Cadmium, Acid Paste • Batteries “add” when you connect them in series. • Circuit Symbol:

  30. Equation for Voltage V=W/Q V = the voltage in volts (V) Q = the amount of charge in Coulombs (C) W = the energy expended in Joules (J)

  31. Example Problem 2.7 • Determine the energy expended by a 12 V battery in moving 20 x 1018 electrons between its terminals.

  32. Example Problem 2.8 • (a) If 8 mJ of energy is expended moving 200 mC from one point in an electrical circuit to another, what is the difference in potential between the two points? • (b) How many electrons were involved in the motion of charge in part (a)?

  33. 2.4 Resistance and Ohm’s Law • Resistance it the measure of a material’s ability to resist the flow of of electrons. • It is measure in Ohms (W). • Ohm’s Law: V = I R V or E = voltage I = current R = resistance

  34. Resistors

  35. Example Problem 2.9 • Determine the voltage drop across a 2.2 kW resistor if the current is 8 mA. Example Problem 2.10 • Determine the current drawn by a toaster having an internal resistance of 22 W if the applied voltage is 120 V.

  36. Example Problem 2.11 • Determine the internal resistance of an alarm clock that draws 20 mA at 120 V.

  37. Equation for Resistance r = resistivity of the material from tables = length of the material in feet (ft) A = area in circular mils (CM) = area of a circle with a diameter of one mil (one thousandth of an inch)

  38. Example Problem 2.12 • Determine the resistance of 100 yards of copper wire having an 1/8 inch diameter. r for copper is 10.37 circular mils/ft (I know, sigh) L = 100 yds = 300 ft ACM = (dmils)2 = (125mils)2 = 15,625 R = rℓ/A = (10.37 CM/ft)(300 ft)/15625 CM R = 0.199 W

  39. Concept Questions • How can you determine the current through a resistor if you know the voltage across it? • I = V/R • How can you change the resistance of a resistor? • Change length, area, or temperature

  40. Resistance depends on Temperature R = resistances t = temperatures a = temperature coefficient from tables

  41. Example Problem 2.15 • The resistance of a copper conductor is 0.3 W at room temperature (20°C). Determine the resistance of the conductor at the boiling point of water (100°C). • R2 = R1[1 + a1(t2 – t1)] • R2 = (0.3 W)[1 + 0.00393(100°-20°)] • R2 = 0.394 W

  42. Four-banded Resistor Five-banded Resistor

  43. Resistor Color Codes 0 Black 1 Brown 2 Red 3 Orange 4 Yellow 5 Green 6 Blue 7 Violet 8 Gray 9 White Tolerance 5% Gold 10% Silver Memorize this table. Calculator

  44. 0 Black 1 Brown 2 Red 3 Orange 4 Yellow 5 Green 6 Blue 7 Violet 8 Gray 9 White Tolerance 5% Gold 10% Silver Example Problem 2.17 • Determine the manufacturer’s guaranteed range of values for a carbon resistor with color bands of Blue, Gray, Black and Gold. • 68 X 100 5% = 68 W  3.4 W Example Problem 2.18 • Determine the color coding for a 100 kW resistor with a 10% tolerance. • 100 kW = 100,000 W • Band 1 (Brown) Band 2 (Black) • Band 3 (Yellow) Band 4 (Silver)

  45. Total Resistance for Resistors in Series Total Resistance for Resistors in Parallel

  46. Potentiometers • They are three terminal devices with a knob. • The knob moves a slider which changes the resistance between the terminals. • Circuit Symbols:

  47. What is the difference between E and V? • E is the voltage supplied by a battery. • V is the voltage measured across a resistor.

  48. 2.5 Power, Energy, Efficiency • Power is the measure of the rate of energy conversion. • Resistors convert electrical energy into heat energy. • Equation for Power: P = I E Power Delivered by a Battery P = I V Power Dissipated by a Resistor • What are some other ways that we can write this equation?