- Circuit theory
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For the theory of monetary economics, see monetary circuit theory.
Circuit theory is the theory of accomplishing work by means of routing matter through a loop.[citation needed] The types of matter used are:
- In electronic or electrical circuits: electrons (and charged ions, both positive and negative)
- In pneumatic circuits: compressed gas (normally ordinary air)
- In hydraulic circuits: pressurized, relatively incompressible fluid
- In magnetic circuits: magnetic flux is channeled through coupled magnetic cores.
Contents
Parts of a circuit
Every circuit consists of three basic components:
- "Active components": Source of energy
- Transmission lines
- Control devices (optional)
- "Passive components": Load
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 blockage 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."
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.
Types
There are four basic types of circuits currently used in industry:
- Electronic or electrical
- Pneumatic
- Hydraulic
- Magnetic
The following is a rough list of the types of components which make up each type of circuit.
Electronic circuit
- Sources of energy
- Transmission lines
- Passive components
Pneumatic circuit
- Sources of energy
- Transmission lines
- Passive components
Hydraulic circuit
- Sources of energy
- Transmission lines
- Hydraulic hoses
- Passive components
See also
- Network analysis (electronics)
- Mesh analysis
- Active component
- Passive component
- Fluid power
- Memristor
- Signal (circuit theory)
References
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