Circuit Theory: Wikis


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Circuit theory is the theory of accomplishing work by means of routing matter through a loop. The types of matter used are:


Parts of a circuit

Every circuit consists of three basic components:

A gun, a rocket and an internal combustion engine all use compressed gas to do work, but the spent gas is vented to the atmosphere and is not reused in the system, so these are not examples of pneumatic circuits. Refrigeration systems do, however, recycle the compressed gases they use, but are not typically thought of as circuits.

Gears, levers, linkages, pulleys/ropes and sprockets/chains transmit work energy from one location to another, but there is no loop, so these are not examples of circuits.

Circuit vs. network

An electrical circuit is a collection of electrical components which accomplish a specific task such as heating, lighting or running a motor. This collection may or may not form a complete topological loop, depending on whether it is presently connected to power, integrated into a larger device or circuit, or damaged.[1][2] Sometimes, it is convenient to speak of an electrical circuit as a network, de-emphasizing the return path. Return paths are sometimes omitted from circuit diagrams, making the resulting graphic visually resemble a network topology rather than some sort of loop topology. See circuit diagram and schematic.

Open circuit vs. closed circuit

A fundamental part of circuit analysis is determining whether the matter has a return path to the power source. If the matter is blocked from returning to the power source, either wholly or partially, the entire assemblage will be prevented from accomplishing work. In an electrical circuit, an open circuit is caused intentionally when a user opens a switch or unintentionally when vibration or mechanical damage severs a wire. In a pneumatic or hydraulic circuit, this occurs when a valve is closed or there is a leak in one of the lines or components.

In electrical circuits, closing a switch creates a closed loop for the electrons to flow through. This is sometimes referred to as "completing the circuit." Other synonyms are also used.

Short circuit

In an electrical or electronic circuit, sometimes an unintended connection is made, such as when insulation is broken, frayed, melted or chewed by rodents, or a technician inserts a metal tool into a live device. When this happens, current bypasses some or all of the components in the circuit, taking a "shorter" path back to the power source. This can lead to excessive current drain, which in turn generates excessive heat, damaging or destroying sensitive parts of the system such as transistors and ICs.


In Graph theory, an edge whose two ends meet is called a loop, which is an entirely different usage of the word. In any kind of circuit, such a loop has no distinct function. An argument can be made that redundant lines for transmission of power do have a function, even if it is only a backup function.


There are three basic types of circuit currently used in industry:

The following is a rough list of the types of components which make up each type of circuit.

Electronic circuit

Pneumatic circuit

Hydraulic circuit

See also

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Up to date as of January 23, 2010

From Wikibooks, the open-content textbooks collection

Circuit Theory



This wikibook is going to be an introductory text about electric circuits. It will cover some of the basics of electric circuit theory, circuit analysis, and will touch on circuit design. This book will serve as a companion reference for a 1st year student of an Electrical Engineering undergraduate curriculum. Topics covered include AC and DC circuits, passive circuit components, phasors, and RLC circuits. Links in blue or purple are existing pages that (should) have content. Red links point to pages that do not yet exist. Entries in black (no link) represent proposed pages.

This book is not nearly completed, and could still use a lot of work. People with knowledge of the subject are encouraged to contribute.

Special Pages

Print Version: Print Version (edit print version) (discuss)

Warning: The print version is over 90 pages long, as of 2 August, 2006.

Cover Page: Cover Page

All Pages: All Pages

Table of Contents

Section 1: Circuit Basics

Section 2: Resistive Circuit Analysis

Section 3: Energy Storage Elements

Section 4: AC Analysis

Section 5: Transforms

Section 6: 3-Phase Power

Section 7: Two Port Networks (Proposed)


Resources and Licensing

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