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Basic Electrical Circuits & Machines (EE-107)

Basic Electrical Circuits & Machines (EE-107). Course Teacher Shaheena Noor Assistant Professor Computer Engineering Department Sir Syed University of Engineering & Technology. Basic Components and Electrical Circuits.

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Basic Electrical Circuits & Machines (EE-107)

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  1. Basic Electrical Circuits & Machines (EE-107) Course Teacher ShaheenaNoor Assistant Professor Computer Engineering Department Sir Syed University of Engineering & Technology.

  2. Basic Components and Electrical Circuits The basic goals of this chapter is to understand the basic electrical quantities (with associated unit), Relationship between charge, current, voltage and power, Difference between dependent and independent sources (both voltage and current) and detailed knowledge of the behavior of the resistor and Ohm’s law.

  3. Basic Components and Electric Circuits • Components • Electric Circuits

  4. Charge, Current, Voltage and Power Charge: • Definition  It is define in terms of ampere by counting the total charge that passes through a wire in one second. • Symbol  Q or q • Unit of Measurement  Coulomb • Unit Abbreviated  C

  5. Charge, Current, Voltage and Power Current: • Definition  Transfer of charge OR transfer energy from one point to another. • For Example  Power transmission line (practical example of transfer energy)

  6. Charge, Current, Voltage and Power • It has numerical value and direction. • Correct Representation  • Two methods of representation for the exact same current. • Improper/incomplete definitions of a current - 3A 3A Figure a Figure b i1(t) i1(t)

  7. Charge, Current, Voltage and Power • Symbol  I or i • Unit of Measurement  Ampere (“Amp”) • Unit Abbreviated  A

  8. Charge, Current, Voltage and Power Types of Current: • A current that is constant in time is termed as Direct Current or simply dc. i t

  9. Charge, Current, Voltage and Power Types of Current: • Current that vary sinusoidally with time; current of this form are present in normal household circuits. Such a current is often referred to as Alternating current or ac. i t

  10. Charge, Current, Voltage and Power Types of Current: • Exponential Currents & Damped Sinusoidal current (will discuss later) i i t t

  11. Drill Problem 2.3 (page 11) • In the wire of the given figure, electrons are moving left to right to create a current of 1mA. Determine I1 and I2. I1 I2

  12. Charge, Current, Voltage and Power Voltage: • Consider an object with 2 terminals. • Two paths by which current may enter or leave the element. A general 2-terminal circuit element A B

  13. Charge, Current, Voltage and Power • Symbol  V or v or E • Unit of Measurement  “Volts” • Unit Abbreviated  V

  14. Charge, Current, Voltage and Power • Inadequate definitions of a voltage • A correct definition + + V1(t) V1(t) - - A correct definition includes both a symbol for the variable and a plus-minus symbol pair.

  15. Charge, Current, Voltage and Power • Voltage: A A A A + - + - V = 5V V = -5V V = 5V V = -5V - + - + B B B B Fig (a) Fig (b) Fig (c) Fig (d) Fig (d)

  16. Charge, Current, Voltage and Power Important Point: • A voltage can exist between a pair of electrical terminals whether a current is flowing or not. • For example  An automobile battery has a voltage of 12V across its terminals even if nothing is connected to the terminals.

  17. Drill Problem 2.4 (page 13) • For the given figure; if V1 = 17V. Determine V2. + V1 - - V2 +

  18. Charge, Current, Voltage and Power Power: • Definition Power is a measure of how much work can be performed in a given amount of time. • In electric circuits, power is a function of both voltage and current. P = VI • Symbol  P or p • Unit of Measurement  Watt • Unit Abbreviated  W

  19. Drill Problem 2.5 (page 15) Find the power being absorbed by the circuit element. + 220mV 4.6A -

  20. Drill Problem 2.6 (page 15) • Find the power being generated by the circuit element. + -3.8V -1.75A -

  21. Drill Problem 2.7 (page 15) • Find the power being delivered by the circuit element at t = 5ms. 8e-100t V + - 3.2A

  22. Voltage and Current Sources • Independent Source • Dependent Source

  23. Voltage and Current Sources Independent Voltage Source + - Vs

  24. Voltage and Current Sources Independent Voltage Source • Other Representations + - Vs Battery Symbol Ac voltage source

  25. Voltage and Current Sources • Independent Current Source Is

  26. Voltage and Current Sources Dependent Sources • Also referred as controlled source. • It is determined by a voltage or current existing at some other location in the system being analyzed. • Symbol  A diamond Shape

  27. Voltage and Current Sources • Four Different types of Dependent Sources + - + - gVx KVx rix Kix Figure (a) Figure (b) Figure (c) Figure (d)

  28. Drill Problem 2.8 (page 18) • Find the power absorbed by each element in the circuit given below. - -Vx + 5A + 8 V - - 12V + + 12 V - + 20 V - + 8 V - 0.25Vx 7 A 8 A 2 A

  29. Ohm’s Law • The voltage across conducting materials is directly proportional to the current flowing through the material. V = I * R • Power: P = V * I • Power Absorption:

  30. Drill Problem 2.9, 2.10 (Page 23) • With reference to V and I defined in the given figure, compute the following quantities. 2.9: R if I = -1.6mA and V = -6.3V 2.10: The absorbed power if V = -6.3V and R = 21Ω figure

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