1. identify various types of electric circuit: dc, ac and dynamic circuits.
2. identify nodes, elements, element parameters, loops and meshes in a circuit diagram.
3. write and solve the equations indicated by Kirchhoff's laws.
4. write and solve the element equations corresponding to the circuit elements.
5. use the passive convention to
   • write correct element equations
   • distinguish the "power supplied" from the "power received" by a circuit element

Remark: The Kirchhoff law equations for ac circuit require special attention.

Reading: Sections 1.1 thru 1.5, 2.4 thru 2.10 and 3.2

• We analyze electric circuits by writing and solving a set of equations.
  • Some of those equation are written using Kirchhoff's laws (Section 3.2).
  • The rest of the equations describe the devices that comprise the circuit. These equations are called "element equations" or "constitutive equations". Ohm's law is the most familiar example of a constitutive equation. Indeed, the constitutive equations are sometimes informally referred to as the "Ohm's law equations." Chapter 2 presents constitutive equations for resistors (Section 2.4), independent sources (Section 2.5), open and short circuits (Section 2.5), dependent sources (Section 2.7), and switches (Section 2.9).

• The passive convention (Sections 1.2-1.5) is important because
  • It's assumed in the element equations.
  • It's involved in our vocabulary regarding electric power (see Table 1.5-1).

• Two seemingly different circuit drawings might represent the same circuit. How can we tell? See Example 3.2-1

Lecture Notes:

• Almost every problem in this course will include a circuit diagram.

• The "answer" to a circuit analysis problem is likely to be an element voltage or current. These element voltages and currents are represented differently it different types of circuit:

  Circuit Type	Current and Voltage Waveform	Voltage and Currents Represented by
  dc		Constant functions represented by real numbers
  ac		Sinusoidal functions of time represented by complex numbers
  first-order		exponential functions of time

  Consequently, it's important that we be able to distinguish the various types of electric circuits.

• Our first challenge is to master the passive convention. Here are some examples and some exercises.

• We analyze electric circuits by writing and solving a set of equations.
  • Some of those equation are written using Kirchhoff's laws. Here are some examples of dc circuit problems that can be solved using Kirchhoff's laws. Here are some exercises.
  • The rest of the equations are element equations. Here's a tabulation of the element equations.

• Here's a nasty surprise. Using Kirchhoff's laws in ac circuits or in dynamic circuits is more work than using Kirchhoff's laws in dc circuits. Here are some examples, including some observations regarding ac circuits. Here are some exercises.

• Handouts:
  • Kirchhoff's laws.
  • Ohm's and Kirchhoff's laws worksheet.
  • Ohm's and Kirchhoff's problems and solutions,
  • How Can We Check... currents and voltages
    • Using Kirchhoff's laws?
    • Using the element equations of the circuit elements?

Demonstrations: Reference Directions

On-line Exercises: Kirchhoff's Laws