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EE 2301 BASIC ELECTRONIC CIRCUIT

EE 2301 BASIC ELECTRONIC CIRCUIT. INSTRUCTOR: DR. ANGUS WU OFFICE: G6352 PHONE: 9391 EMAIL: angus.wu@cityu.edu.hk URL: www.ee.cityu.edu.hk/~ee2301 ID: ee2301 passwd: ee2301. LECTURE 1. Fundamentals. Charge, Current, Voltage Ohm’s Law and Power

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EE 2301 BASIC ELECTRONIC CIRCUIT

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  1. EE 2301 BASIC ELECTRONIC CIRCUIT

  2. INSTRUCTOR: DR. ANGUS WU OFFICE: G6352 PHONE: 9391 EMAIL: angus.wu@cityu.edu.hk URL: www.ee.cityu.edu.hk/~ee2301 ID: ee2301 passwd: ee2301

  3. LECTURE 1

  4. Fundamentals Charge, Current, Voltage Ohm’s Law and Power Series Circuits and Kirchhoff’s Voltage Law Parallel Circuits and Kirchholf’s Current Law Resistive Circuits Circuit Analysis Techniques

  5. Charge

  6. The Starting Point: Elements, Atoms and Charge

  7. Charge Force that causes two particles to be attracted to, or repelled from, each other Two types – positive and negative Atom – proton (positive), electron (negative), neutron (electrically neutral) Charge

  8. Attraction and Repulsion - Like charges repel each other and opposite charges attract each other Ions Outside force can cause an electron to leave its orbit -atom is referred to as a positive ion Outside force can cause an atom to gain an electron -atom is referred to as a negative ion Free Electrons An electron that is not bound to any particular atom Can neutralize a positive ion

  9. Current

  10. Current – the directed flow of charge through a conductor Thermal energy (heat) is sufficient to free electrons in copper Free electron motion is random unless outside force is applied Current

  11. Represented by the letter i (for intensity) Measured in charge per unit time Current where i = the intensity of the current dq = the amount of charge dt = the time (in seconds) required for the charge (dq) to pass

  12. Coulomb (C) – represents the total charge of approximately 6.25 x 1018 electrons Unit of Current – Ampere (A) = 1 coulomb/second Example: 3 coulombs of charge pass a point in a wire every two seconds. Calculate current. Current

  13. Electrical current is the time rate of flow of electrical charge through a conductor or circuit element. The units are amperes (A), which are equivalent to coulombs per second (C/s). Electrical Current

  14. Electrical Current

  15. Electron Flow Versus Conventional Current Electrical Current Insert Figure 1.10

  16. When a current is constant with time, we say that we have direct current, abbreviated as dc. On the other hand, a current that varies with time, reversing direction periodically, is called alternating current, abbreviated as ac. Direct Current Alternating Current

  17. Figure 4.17, 4.18

  18. .

  19. Two different methods of labeling the same current. (a,b) Incomplete, improper, and incorrect definitions of a current. (c) the correct definition of i1(t).

  20. Current Insert Figure 1.11

  21. Voltage

  22. The voltage associated with a circuit element is the energy transferred per unit of charge that flows through the element. The units of voltage are volts (V), which are equivalent to joules per coulomb (J/C). Voltage

  23. Voltage – a “difference of potential” that generates the directed flow of charge (current) through a circuit Voltage Insert Figure 1.12

  24. Often referred to as electromotive force (emf) Unit of Voltage – volt (V) = 1 joule/coulomb Volt – the difference of potential that uses one joule of energy to move one coulomb of charge. Voltage

  25. (a, b) These are inadequate definitions of a voltage. (c) A correct definition includes both a symbol for the variable and a plus-minus symbol pair. (a, b) Terminal B is 5 V positive with respect to terminal A; (c,d) terminal A is 5 V positive with respect to terminal B.

  26. Various representations of an electrical system Ideal voltage sources

  27. Symbol for ideal current source

  28. Ohm’s Law and Power

  29. German Physicist – George Simon Ohm Found that current is inversely proportional to resistance for a given voltage Known as Ohm’s law The Relationship Between Current and Voltage The Relationship Between Current and Resistance Ohm’s Law

  30. Using Ohm’s Law to Calculate Current Basic Circuit Calculations where R = the circuit resistance V = the applied voltage

  31. Using Ohm’s Law to Calculate Voltage Basic Circuit Calculations where I = the circuit current R = the circuit resistance

  32. Using Ohm’s Law to Calculate Resistance Basic Circuit Calculations where V = the circuit voltage I = the circuit current

  33. Resistance Element

  34. Power – the amount of energy used per unit time Unit of Power – Watt (W) = 1 joule/second Calculating Power Power P = IV where P = the power used, in watts (W) V = the applied voltage, in volts (V) I = the generated current, in amperes (A)

  35. Other Power Equations Use IR in place of V Use V/R in place of I Power

  36. If the current arrow is directed into the “ +” marked terminal of an element, then p = vi yields the absorbed power. A negative value indicates that power is actually being generated by the element. If the current arrow is directed outof the “ +” terminal of an element, then p = vi yields the supplied power. A negative value in this case indicates that power is actually being absorbed instead of generated.

  37. Passive Sign Conversion

  38. POWER AND ENERGY instantaneous power

  39. Power and Heat Resistors and other components convert energy to heat (transducer) If power rating is exceeded, the component will keep getting hotter and be destroyed Common guideline – select a component with twice the required power-dissipation capability Power

  40. Efficiency – the ratio of a circuit or components output power to its input power Power where  = the efficiency, as a percentage Po = the output power Pi = the input power

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