CPAC LECTURE 1

• Electric Charge


  An electrical property of the atomic particles of which matter consists, measured in coulombs (C)
• The coulomb is a large unit for charges. In 1 C of charge, there are 6.24 x 10^18 electrons. Realistic or laboratory values of charges are on the order of pC, nC, or μC.
• According to experimental observations, the only charges that occur in nature are integral multiples of the electronic charge.
• The law of conservation of charge states that charge can neither be created nor destroyed, only transferred. The algebraic sum of the electric charges in a system does not change.
• Electric current due to flow of electronic charge in a conductor

  1. Positive charges move in one direction

  2. Negative charges move in the opposite direction
• Electric current


  The time rate of change of charge, measured in amperes (A)
• Direct current


  A current that remains constant with time
• Alternating current


  A current that varies sinusoidally with time
• The direction of current flow is conventionally taken as the direction of positive charge movement
• A negative current of -5A flowing in one direction is the same as a current of +5A flowing in the opposite direction
• Voltage (or potential difference)


  The energy required to move a unit charge through an element, measured in volts (V)
• A voltage drop from a to b is equivalent to a voltage rise from b to a
• DC voltage


  A constant voltage
• AC voltage


  A sinusoidally time-varying voltage
• Power


  The time rate of expending or absorbing energy, measured in watts (W)
• Passive sign convention


  Power is positive when current enters through the positive terminal of an element (Power being Absorbed)
• Active sign convention


  Power is negative when current enters through the negative terminal of an element (Power being Supplied)
• The law of conservation of energy must be obeyed in any electric circuit. The algebraic sum of power in a circuit is zero.
• Passive sign convention


  Satisfied when the current enters through the positive terminal of an element and p = +vi. vi > 0 implies that the element is absorbing power.
• Active sign convention


  Current enters through the negative terminal, p = -vi, thus the element is supplying power. vi < 0 implies that the element is supplying power.
• Power absorbed


  • Power that has been delivered
• The law of conservation of energy must be obeyed in any electric circuit. The algebraic sum of power in a circuit, at any instant of time, must be zero: Σp = 0
• EnergyWatt-hours (Wh) is equal to how many joules


  3600 J
• Attributes of Ideal basic circuit element

  • Has only two terminals
  • Described mathematically in terms of current and/or voltage
  • Cannot be subdivided into other elements
• Passive element


  Not capable of generating energy
• Active element


  Capable of generating energy
• Independent source


  Provides a specified voltage or current that is completely independent of other circuit elements
• Dependent (or controlled) source

  The source quantity is controlled by another voltage or current
• Types of dependent sources

  • Voltage-controlled voltage source (VCVS)
  • Current-controlled voltage source (CCVS)
  • Voltage-controlled current source (VCCS)
  • Current-controlled current source (CCCS)
• International System of units


  Enables engineers to communicate in a meaningful way about quantitative results
• Voltage


  Energy per unit charge created by charge separation, has the SI unit of volt
• If p < 0


  Power is being delivered to the circuit or circuit component
• Voltage and current sources

  Either independent (not influenced by any other current or voltage in the circuit) or dependent (determined by some other current or voltage in the circuit)
• Active element


  Models a device capable of generating electric energy
• DCmeans


  Direct Current
• Prefix - pico

  • Symbol - P
  • Power - raised to -12
• Electric Circuit

  Interconnection of electrical elements
• Energy


  It is the capacity to do work
• Formula for work 


  $W=$$pt$
• Formula for Charge


  $Q=$$∫𝑖𝑑𝑡$