Chapter 1: The Circuit Abstraction

Electrical Engineering

Using electromagnetic principles to design electrical devices and systems.

Maxwell’s Equations

Equations that describe how electric and magnetic fields behave.

Abstraction

A simplified model that keeps important details while ignoring unnecessary complexity.

Discretization

Representing a continuous system using separate values, ranges, or elements.

Lumped Circuit Abstraction

A circuit model that treats components as separate elements connected by ideal wires.

Lumped Element

A circuit component with clearly defined terminal voltage and current.

Ideal Wire

A wire with zero resistance and zero voltage drop.

Lumped Matter Discipline

The conditions required for the lumped circuit model to be accurate.

Terminal

A connection point where an element connects to a circuit.

Port

A paired group of terminals used to access an electrical element.

Node

A point where two or more element terminals are connected.

Voltage

Energy required to move electric charge between two points.

Volt

The unit of voltage; one joule of energy per coulomb of charge.

Current

The rate at which electric charge flows.

Ampere

The unit of current; one coulomb of charge per second.

Resistance

Opposition to electric current.

Ohm’s Law

The relationship stating that voltage equals current times resistance in an ideal linear resistor.

Resistivity

A material property that measures how strongly the material resists current.

Open Circuit

A path with no current flow.

Short Circuit

A path with zero voltage drop.

Linear Resistor

A resistor whose voltage is proportional to its current.

Nonlinear Resistor

A resistor whose voltage and current are not proportional.

Time-Invariant Resistor

A resistor with constant resistance.

Time-Varying Resistor

A resistor whose resistance changes over time.

Conductance

The ability of a component to allow current flow; the reciprocal of resistance.

Siemens

The unit of conductance.

Power

The rate at which energy is transferred.

Watt

The unit of power; one joule per second.

Energy

The ability to do work or transfer power over time

Joule

The unit of energy.

Associated Variables Convention

The convention where current enters the terminal marked positive for voltage.

Power Dissipation

Conversion of electrical energy into heat or another non-recoverable form.

Battery

A source that converts chemical energy into electrical energy.

Internal Resistance

Resistance inside a battery that reduces its terminal voltage under load.

Ideal Voltage Source

A source that maintains a fixed voltage regardless of current.

Independent Source

A source whose value does not depend on another circuit variable.

Dependent Source

A source controlled by another voltage or current in the circuit.

Ideal Current Source

A source that maintains a fixed current regardless of voltage.

Element Law

An equation relating the voltage and current of a circuit element.

Analog Signal

A signal that can take any value in a continuous range.

Digital Signal

A signal represented by separate, distinct value levels.

Binary Representation

A digital system that uses two levels, usually called zero and one.

Sinusoidal Signal

A repeating signal with a smooth sine-wave shape.

Amplitude

The maximum size of a signal relative to its reference level.

Angular Frequency

The rate at which a sinusoidal signal cycles, measured in radians per second.

Phase Offset

The horizontal shift of a periodic signal relative to a reference.

RMS Value

The equivalent DC value that produces the same average power as a varying signal.

Sheet Resistance

The resistance of a square section of a thin planar material.