A electrical circuit is a closed loop where electrons can flow through. They are used to power things from our microwave to our computer.

Ideal Circuit elements: Used to model real physical components

Series vs. Parallel Connection

Series Connection

Two elements are called connected in series if they are the only two elements connected to a node. Series connected elements have the same current ().

Parallel Connection

Two or more elements are connected in parallel if they are connected between the same two nodes. Parallel-connected elements have the same voltage.

Active vs. Passive Components

Passive Components

Passive components are made to receive energy from active components. They do not require any form of external electrical power to operate.

List of passive components:

Not sure: Potentiometer Crystal Oscillator Resonator

Active Components

Electronic component that supplies energy to a circuit.

Common examples of active components include:

  • Voltage sources
  • Current sources
  • Generators (such as alternators and DC generators)
  • Transistor
  • Diode


Dependent/controlled sources

Electronic devices (such as transistors or amplifiers) are modeled by a dependent / controlled voltage source.

  • A diamond shape is used to indicate a dependent source.

Circuit Elements and Diagrams

We use circuit diagrams to provide a more abstract picture of reality in analyzing and describing circuits. A circuit diagram is a logical picture of what is connected to what.

Circuit Symbols