en>Anaxial: /* Types of ciphers */ formatting

2014-12-23T20:38:02Z

Types of ciphers: formatting

← Older revision		Revision as of 22:38, 23 December 2014
Line 1:		Line 1:
	~~'''Electrical elements''' are conceptual abstractions representing [[idealized]] [[electrical component]]s, such as [[resistor]]s, [[capacitor]]s, and [[inductor]]s, used in~~ the [[circuit analysis\|analysis]] of [[electrical network]]s. Any electrical network can be analysed as multiple, interconnected electrical elements in a [[Schematic diagram#Electronic industry\|schematic diagram]] or [[circuit diagram]], each of which affects the [[voltage]] in the network or [[Current (electricity)\|current]] through the network. These ideal electrical elements represent real, physical [[Electronic component\|electrical or electronic components]] but they do not exist physically and they are assumed to have ideal properties according to a [[lumped element model]], while components are objects with less than ideal properties, a degree of uncertainty in their values and some degree of nonlinearity, each of which may require a combination of multiple electrical elements in order to approximate its function.		The one who wrote the article is called Lida. Releasing output is her day-job currently and her pay has been definitely fulfilling. Her husband and her livein West Virginia. Kayaking is what she loves doing.<br><br>My web page: [http://www.linkedin.com/pub/jordan-kurland/a/618/581 Jordan Kurland]

	~~Circuit analysis using electric elements~~ is ~~useful for understanding many practical electrical networks using components~~. ~~By analyzing the way a network is affected by its individual elements it is possible to estimate how a real network will behave.~~

	~~==One-port elements==~~
	~~Only nine types of element ([[memristor]] not included), five passive and four active, are required to model any electrical component or circuit.{{Citation needed\|date=March 2012}}~~ Each element is defined by a relation between the [[state variable]]s of the network: [[Current (electricity)\|current]], <math>I</math>; [[voltage]], <math>V</math>, [[Electric charge\|charge]], <math>Q</math>; and [[magnetic flux]], <math>\Phi</math>.

	* Two sources:
	**[[Current source]], measured in [[ampere]]s – produces a current in a conductor. Affects charge according to the relation <math>dQ = -I\,dt</math>.
	**[[Voltage source]], measured in [[volt]]s – produces a [[potential difference]] between two points. Affects magnetic flux according to the relation <math>d\Phi = V\,dt</math>.
	::<math>\Phi</math> in this relationship does not necessarily represent anything physically meaningful. In the case of the current generator, <math>Q</math>, the time integral of current, represents the quantity of electric charge physically delivered by the generator. Here <math>\Phi</math> is the time integral of voltage but whether or not that represents a physical quantity depends on the nature of the voltage source. For a voltage generated by magnetic induction it is meaningful, but for an electrochemical source, or a voltage that is the output ~~of another circuit, no physical meaning~~ is ~~attached to it.~~
	~~::Both these elements are necessarily non~~-~~linear elements. See [[#Non-linear elements]] below.~~

	* Three [[Passivity (engineering)\|passive]] elements:
	**[[Electrical resistance\|Resistance]] <math>R</math>, measured in [[Ohm (unit)\|ohms]] – produces a voltage proportional to the current flowing through the element. Relates voltage and ~~current according to the relation <math>dV = R\,dI</math>.~~
	**[[Capacitance]] <math>C</math>, measured in [[farad]]s – produces a current proportional to the rate of change of voltage across the element. Relates charge and voltage according to the relation <math>dQ = C\,dV</math>.
	**[[Inductance]] <math>L</math>, measured in [[Henry (unit)\|henries]] – produces the magnetic flux proportional to the rate of change of current through the element. Relates flux and current according to the relation <math>d\Phi = L\,dI</math>.

	* Four abstract active elements:
	** Voltage-controlled voltage source (VCVS) Generates a voltage based on another voltage with respect to a specified gain. (has ~~infinite input impedance and zero output impedance).~~
	** Voltage-controlled current source (VCCS) Generates a current based on a voltage elsewhere in the circuit, with respect to a specified gain, used to model [[field-effect transistor]]s and [[vacuum tube]]s (has infinite input impedance and infinite output impedance). ~~The gain is characterised by a [[transfer conductance]] which will have units of [[Siemens (unit)\|siemens]].~~
	** Current-controlled voltage source (CCVS) Generates a voltage based on an input current elsewhere in the circuit with respect to a specified gain. (has zero input impedance and zero output impedance). The gain is characterised by a [[transfer impedance]] which will have units of [[ohm]]s.
	** Current-controlled current source (CCCS) Generates a current based on an input current and a specified gain. Used to model [[bipolar junction transistor]]s. (Has zero input impedance and ~~infinite output impedance).~~
	~~::These four elements are examples of [[#Two-port elements\|two-port elements]].~~

	~~===Non-linear elements===~~
	In reality, all circuit components are non-linear and can only be approximated to linear over a certain range. To more exactly describe the passive elements, their [[constitutive relation]] is used instead of simple proportionality. From any two of the circuit variables there are six constitutive relations that can be formed. ~~From this it~~ is supposed that there is a theoretical fourth passive element since there are only five elements in total (not including the various dependent sources) found in linear network analysis. This additional element is called [[memristor]]. It only has any meaning as a time-dependent non-linear element; as a time-independent linear element it reduces to a regular resistor. The constitutive relations of the passive elements are given by;<ref name=Trajkovic>Ljiljana Trajković, "Nonlinear circuits", ''The Electrical Engineering Handbook'' (Ed: Wai-Kai Chen), pp.~~75–77, Academic Press, 2005 ISBN 0-12-170960-4</ref>~~

	*Resistance: constitutive relation defined as <~~math~~>~~f(V, I)=0~~<~~/math~~>.
	*Capacitance: ~~constitutive relation defined as <math>f(V, Q)=0</math>.~~
	*Inductance: constitutive relation defined as <math>f(\Phi, I)=0</math>.
	*Memristance: constitutive relation defined as <math>f(\Phi, Q)=0</math>.

	~~:where <math>f(x,y)</math> is an arbitrary function of two variables.~~

	In some special cases the constitutive relation simplifies to a function of one variable. This is the case for all linear elements, but also for example, an ideal [[diode]], which in circuit theory terms is a non-linear resistor, has a constitutive relation of the form <math> V = f(I)</math>. Both independent voltage, and independent current sources can be considered non-linear resistors under this definition.<ref name=Trajkovic/>

	The fourth passive element, the memristor, was proposed by [[Leon Chua]] in a 1971 paper, but a physical component demonstrating memristance was not created until thirty-seven years later. It was reported on April 30, 2008, that a working memristor had been developed by a team at [[HP Labs]] led by scientist [[R. Stanley Williams]].<ref>{{citation\|last=Strukov\|first=Dmitri B\|last2=Snider\|first2=Gregory S\|last3=Stewart\|first3=Duncan R\|last4=Williams\|first4=Stanley R\|title=The missing memristor found\|journal=Nature\|volume=453\|pages=80–83\|year=2008\|doi=10.1038/nature06932\|url=http://www.nature.com/nature/journal/v453/n7191/full/nature06932.html\|pmid=18451858\|issue=7191\|bibcode=2008Natur.453...80S}}</ref><ref>EETimes, 30 April 2008, [http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=207403521 'Missing link' memristor created], EETimes, 30 April 2008</ref><ref>[http://technology.newscientist.com/article/dn13812-engineers-find-missing-link-of-electronics.html Engineers find 'missing link' of electronics] – 30 April 2008</ref><ref>[http://www.~~physorg~~.com/news128786808.html Researchers Prove Existence of New Basic Element for Electronic Circuits – 'Memristor'] – 30 April 2008</ref> With the advent of the memristor, each pairing of the four variables can now be related. Because memristors are time-variant by definition, they are not included in [[LTI system theory\|linear time-invariant (LTI)]] circuit models.{{cn\|reason=they are not included because they are not linear surely. It is perfectly feasible to have a time invariant memristor as a theoretical ideal element\|date=May 2013}}

	~~There are also two special non-linear elements which are sometimes used in analysis but which are not the ideal counterpart of any real component:~~

	*[[Nullator]]: defined as <math> V = I = 0 </math>
	*[[Norator]]: defined as an element which places no restrictions on voltage and current whatsoever.

	~~These are sometimes used in models of components with more than two terminals: transistors for instance.<ref name=Trajkovic~~/>

	~~==Two-port elements==~~
	All the above are two-terminal, or one-port, elements with the exception of the dependent sources. There are two lossless, passive, linear [[two-port network\|two-port]] elements that are normally introduced into network analysis. Their constitutive relations in matrix notation are;

	~~;Transformer:~~

	~~: <math> \begin{bmatrix} V_1 \\ I_2 \end{bmatrix} = \begin{bmatrix} 0 & n \\ -n & 0 \end{bmatrix}\begin{bmatrix} I_1 \\ V_2 \end{bmatrix}</math>~~

	~~;Gyrator:~~

	~~: <math> \begin{bmatrix} V_1 \\ V_2 \end{bmatrix} = \begin{bmatrix} 0 &~~ -~~r \\ r & 0 \end{bmatrix}\begin{bmatrix} I_1 \\ I_2 \end{bmatrix}</math>~~

	~~The transformer maps a voltage at one port to a voltage at the other in a ratio of ''n''. The current between the same two port is mapped by 1~~/''n''. The [[gyrator]], on the other hand, maps a voltage at one port to a current at the other. Likewise, currents are mapped to voltages. The quantity ''r'' in the matrix is in units of resistance. The gyrator is a necessary element in analysis because it is not [[Reciprocity_(electromagnetism)#Reciprocity_for_electrical_networks\|reciprocal]]. Networks built from the basic linear elements only are obliged to be reciprocal and so cannot be used by themselves to represent a non-reciprocal system. It is not essential, however, to have both the transformer and gyrator. Two gyrators in cascade are equivalent to a transformer but the transformer is usually retained for convenience. Introduction of the gyrator also makes either capacitance or inductance non-essential since a gyrator terminated with one of these at port 2 will be equivalent to the other at port 1. However, transformer, capacitance and inductance are normally retained in analysis because they are the ideal properties of the basic physical components [[transformer]], [[inductor]] and [[capacitor]] whereas a [[Gyrator#Implementation: a simulated inductor\|practical gyrator]] must be constructed as an active circuit.<ref>Wadhwa, C.L., ''Network analysis and synthesis'', pp.17–22, New Age International, ISBN 81-224-1753-1.</~~ref><ref>Herbert J. Carlin, Pier Paolo Civalleri, ''Wideband circuit design'', pp.171–172, CRC Press, 1998 ISBN 0-8493-7897-4.<~~/~~ref><ref>Vjekoslav Damić, John Montgomery, ''Mechatronics by bond graphs: an object-oriented approach to modelling and simulation'', pp.32–33, Springer, 2003 ISBN 3-540-42375-3.</ref>~~

	~~==Examples==~~
	~~The following are examples of representation of components by way of electrical elements.~~
	* On a first degree of approximation, a [[battery (electricity)\|battery]] is represented by a voltage source. A more refined model also includes a resistance in series with the voltage source, to represent the battery's internal resistance (which results in the battery heating and the voltage dropping when in use). A current source in parallel may be added to represent its leakage (which discharges the battery over a long period of time).
	* On a first degree of approximation, a [[resistor]] is represented by a resistance. A more refined model also includes a series inductance, to represent the effects of its lead inductance (resistors constructed as a spiral have more significant inductance). A capacitance in parallel may be added to represent the capacitive effect of the proximity of the resistor leads to each other. A wire can be represented as a low-value resistor
	* Current sources are more often used when representing [[semiconductor]]s. For example, on a first degree of approximation, a bipolar [[transistor]] may be represented by a variable current source that is controlled by the input current.

	~~==See also==~~
	~~{{Commons\|Electronic devices}}~~
	* [[Electronic component]]
	* [[Lumped element model]]
	* [[Distributed element model]]
	* [[Transmission line]]

	~~==References==~~
	~~{{Reflist}}~~

	~~{{DEFAULTSORT:Electrical Element}}~~
	~~[[Category:Electronics]]~~
	~~[[Category:Electrical systems]]~~

	~~[[ar:عنصر كهربائي]]~~
	~~[[ta:மின் உறுப்புகள்]~~]

en>Haeinous at 11:08, 12 July 2013

2013-07-12T11:08:35Z

Show changes

en>Akbarisaeed at 15:47, 13 July 2012

2012-07-13T15:47:49Z

New page

The net is providing a lot of companies the chance to achieve a lot more buyers then before. We are within the information age today and meaning they is plenty of ways for firms to acquire their services or products to their clients. A great deal of income generating e-mails have now been thrown down the drain as a result of spam filters. The main element would be to inform your members to "Whitelist" and likewise, online entrepreneurs must stop from giving "Spammy" emails which includes "Spam Words" such as "Free" and "Generate Income Online". Referrals are simple to get. I've above a 100 and I've spent very little time looking to get recommendations and all of it extends back to reason number one. Since it's free folks are prepared to join and at the least attempt it, which leads me to my next reason. Advertising Networks is really a single point of contact where you have use of many different websites to place your advertisements. In the place of independently seeking these sites out. You are in a position to access various them on a single system. Moreover, you are billed using one invoice for almost any options that you've picked. After you've constructed an excellent enough marketing knowledge-base, you should market yourself as a way to get customers. You should employ [http://20thstreetblockparty.com/2014/jordan-kurland-intro/ Jordan Kurland], that would be appropriate for smallbusiness and increase your internet site, also. Google AdSense and AdWords could possibly be put to good use within this scenario! I'm-not saying everyone reading this post is going out there and start their own delivery company that moves odd items but I do believe that everyone out there can carve out their own little niche. If you seek for Shipment Battles News you will realize that there are a lot of men and women searching for this online. Much like there are a million people out there looking for actually random junk. This junk will become gold for you, If you are great at this. Additionally, it's free! You don't need certainly to pay extremely high fees just to get your internet site off the floor to a web designer. You can create your WordPress site entirely for free, generating WordPress exceedingly costeffective for your website needs. The only real price is to get a domain and hosting, which can be minimal. Deyrolle store is the place where you can buy a stuffed elk, a frogIs skeleton and you can also view many creatures of styles including geese, rabbits, foxes, butterflies and so on.

Ciphertext - Revision history

en>Anaxial: /* Types of ciphers */ formatting

en>Haeinous at 11:08, 12 July 2013

en>Akbarisaeed at 15:47, 13 July 2012