Содержание
- 2. Symbol: (q) Unit: Coulomb (C) The fundamental electric quantity is charge. Atoms are composed of charge
- 3. Current Current moves through a circuit element “through variable.” Current is rate of flow of negatively-charged
- 4. Current-Water Analogy
- 5. Voltage Potential difference across two terminals in a circuit “across variable.” In order to move charge
- 6. Voltage-Water Analogy
- 7. Voltage/Current-Water Analogy
- 8. Series Connection of Cells Each cell provides 1.5 V Two cells connected one after another, in
- 9. Parallel Connection of Cells If the cells are connected in parallel, the voltage stays at 1.5
- 10. Wire-Water Analogy
- 11. Resistor Concept —I Flow of electric current through a conductor experiences a certain amount of resistance.
- 12. Resistor Concept —II A resistor is a dissipative element. It converts electrical energy into heat energy.
- 13. Resistors-Water Analogy
- 14. Resistor V-I Characteristic In a typical resistor, a conducting element displays linear voltage-current relationship. (i.e., current
- 15. Resistor Applications Resistors are used for: Limiting current in electric circuits. Lowering voltage levels in electric
- 16. Resistors: Power Rating and Composition It is very important to be aware of power rating of
- 17. Resistor Examples
- 18. Resistor Labels Wire-wound resistors have a label indicating resistance and power ratings. A majority of resistors
- 19. Resistor Color Codes x.01 - Silver X1000000000 9 White X100000000 8 Grey X10000000 7 Purple X1000000
- 20. Example The first band is yellow, so the first digit is 4 The second band is
- 21. Metric Units and Conversions Abbreviation Means Multiply unit by Or p pico .000000000001 10 -12 n
- 22. Digital Multimeter 1 DMM is a measuring instrument An ammeter measures current A voltmeter measures the
- 23. Digital Multimeter 2 Voltmeter Parallel connection Ammeter Series connection Ohmmeter Without any power supplied Adjust range
- 24. Ammeter Connection Break the circuit so that the ammeter can be connected in series All the
- 25. Voltmeter Connection The voltmeter is connected in parallel between two points of circuit A voltmeter should
- 26. Ohmmeter Connection An ohmmeter does not function with a circuit connected to a power supply Must
- 27. Resistors in Series Rtotal=R1+R2 Rtotal=1+1=2kΩ
- 28. Resistors in Parallel
- 29. Exercise 1
- 30. Variable Resistor Concept In electrical circuit, a switch is used to turn the electricity on and
- 31. Variable Resistor Construction To vary the resistance in an electrical circuit, we use a variable resistor.
- 32. Variable Resistor Operation The dial on the variable resistor moves the arm contact and sets the
- 33. Variable Resistor: Rotary Potentiometers
- 34. Variable Resistor: Other Examples Photoresistor Thermistor
- 35. Resistance Formula
- 36. Capacitor Concept A capacitor is an energy storage element which is analogous to the spring element
- 37. Capacitor Construction A capacitor is constructed using a pair of parallel conducting plates separated by an
- 38. Capacitor Water Pipe Analogy —I In the water pipe analogy, a capacitor is thought of as
- 39. Capacitor Water Pipe Analogy —II If the rubber diaphragm is made very soft, it will stretch
- 40. Capacitor Water Pipe Analogy —III Water capacitor: a tube with a rubber membranne in the middle
- 41. Capacitor V-I Characteristic The charge accumulated on capacitor plates is directly proportional to voltage applied across
- 42. Capacitance Formula For a parallel capacitor: - ε0 = permittivity of free space - A =
- 43. Capacitor Symbols
- 44. Capacitor Variations Ceramic capacitors very popular nonpolarized capacitor small, inexpensive, but poor temperature stability and poor
- 45. Capacitor Variations Mylar very popular, nonpolarized reliable, inexpensive, low leakage poor temperature stability Mica extremely accurate,
- 46. Capacitor Reading Example —I Thus, we have a 0.1μF capacitor with ±10% tolerance.
- 47. Capacitor Reading Example —II
- 48. Variable Capacitors Devices that can be made to change capacitance values with the twist of a
- 49. Inductors For an ideal coil, magnetic flux is proportional to current, so ∝ I or λ
- 50. Inductor-Water Analogy —I Suppose a turbine is hooked up to the flywheel and water is supplied
- 51. Inductor-Water Analogy —II When switch S contacts A, the field generated by the applied positive voltage
- 52. Inductance of a Cylindrical Coil If number of turns per unit length is “n”, then N=
- 53. Inductor Variations —I
- 54. Inductor Variations —II Antenna coil contains an iron core that magnifies magnetic field effects used to
- 55. Inductor Variations —III Chokes general-purpose inductors that act to limit or suppress fluctuating current. some use
- 56. Inductor Symbols
- 57. Transformer Isolation acts exclusively as an isolation device; does not increase or decrease the secondary voltage
- 58. Kirchoff’s Voltage Law The algebraic sum of voltage around a loop is zero. Assumption: Voltage drop
- 59. Kirchoff’s Current Law Algebraic sum of all currents entering and leaving a node is zero. At
- 60. Law of Voltage division
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