Essential Information & explanations, latest texts & monographs on
Electrical_current.
The Design and Evaluation of Physical Protection Systems by Mary Lynn Garcia
Your Old Wiring by David E. Shapiro
Switching Power Supply Design by Abraham I. Pressman
Electrician's Pocket Manual by Rex Miller
Low Voltage Wiring: Security/Fire Alarm Systems by Terry Kennedy
The Complete Book of Electronic Security by Bill Phillips
Power Electronics : Converters, Applications, and Design by Ned Mohan
LAN Wiring: An Illustrated Guide to Network Cabling by James Trulove
Cabling Handbook, The (2nd Edition) by John R. Vacca
Alternating Current Fundamentals by John R. Duff
Rating of Electric Power Cables: Ampacity Computations for Transmission, Distribution, and Industrial Applications by George J. Anders
Grounding and Shielding Techniques by Ralph Morrison
Grounding and Shielding Techniques in Instrumentation by Ralph Morrison
Principles of Electric Circuits: Conventional Current Version (7th Edition) by Thomas L. Floyd
Pulse Width Modulation for Power Converters : Principles and Practice by D. Grahame Holmes
Current (electricity)(Redirected from Electrical current)
Electromagnetism
Electricity
Electric charge
Coulomb's law
Electromagnetic field
Gauss's law
Electric potential
Electric current
Resistance
Electromotive force
Magnetism
Magnetic field
Ampere's law
Induction
Faraday's law
Maxwell's equations
In electricity, current is any flow of charge, usually through a metal wire or some other electrical conductor. Conventional current was defined early in the history of electrical science as a flow of positive charge, although we now know that, in the case of metallic conduction, current is caused by a flow of negatively charged electrons in the opposite direction. Despite this understanding, the original definition of conventional current still stands. The symbol typically used for the amount of current (the amount of charge flowing per unit of time) is I. Historically, the symbol for current, I, came from the German word Intensität, which means 'intensity'. The SI unit of electrical current is the ampere. Electric current is therefore sometimes informally referred to as amperage, by analogy with the term voltage. However, engineers frown on this usage, which is considered amateurish.
Current density is the current per unit (cross-sectional) area.
In metallic conductors, such as wires, currents are caused by a flow of electrons (negatively charged particles), but this is not case in most non-metallic conductors. Electric currents in electrolytes are flows of electrically charged atoms (ions), which exist in both positive and negative varieties. For example, an electrochemical cell may be constructed with salt water (a solution of sodium chloride) on one side of a membrane and pure water on the other. The membrane lets the positive sodium ions pass, but not the negative chlorine ions, so a net current results. Electric currents in plasma are flows of electrons as well as positive and negative ions. In water ice and in certain solid electrolytes, flowing protons constitute the electric current.
There are also instances where the electrons are the charge that is physically moving, but where it makes more sense to think of the current as the positive "holes" (the spots that should have an electron to make the conductor neutral) as being what moves. This is the case in a p-type semiconductor.
See electrical conduction for more information on the physical mechanism of current flow in materials.
Mathematically, current is defined as the net flux through an area. Thus:
\phi = j \cdot A
">
where A is the area through which the current is flowing, φ is the current, and j is called the "current density". The current density is defined as:
j=\int_i n_i \cdot x_i \cdot \mathbf{u_i}
">
where n is the particle density (number of particles per unit volume), u is the average velocity of the particles in each volume, and x can be mass, charge, or any other characteristic whose flow one would like to measure.
Every electric current produces a magnetic field. The magnetic field can be visualized as a pattern of circular field lines surrounding the wire.
Electric current can be directly measured with a galvanometer, but this method involves breaking the circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field it creates. Devices used for this include Hall effect sensors, current clamps and Rogowski coils.
Ohm's Law predicts the current in an (ideal) resistor (or other ohmic device) to be the quotient of applied voltage over electrical resistance:
I = \frac{V}{R}
">
See also: Alternating current, Direct current
The above article is adapted from from Wikipedia All Wikipedia article text is available under the terms of the GNU Free Documentation License
Updates and comments at Essential Facts blog
World Class Photographers
Some philosophical movements
|
|
Interesting Links
Latest Dowloadable
Electrical_current PDF s & Ebooks
Top PDF and eBook Downloads
Bibliographic Resources
Dates
20-th Century
20-th Century Details
Chromosomes and Genomics
Sports
Kitchen Knowledge
Hollywood Icons
Classical Music
Music Directory.
Music: Jazz
Music: Rock
Music: Country
Music: Popular A-E
Music: Popular F-L
Music: Popular M-S
Music: Popular T-Z
Mythology
Philosophy
Politics
Retirement
Agriculture
Agriculture: Flowers
Agriculture: Gardening
Biology
Biology & Biologists
Cell Science
Cell Science: Cells
Cell Science: Stem Cells
California
Cats & Dogs
Ethics
Electronics
Logic
The Greats
Architectural Dates & Places
Styles ABC
Styles DTOI
Styles JTON
Styles OTOZ
Buddhism
Marketing
Psychology
Enginering Systems 1
Mathematics
Classic Authors
Fear No Exams
Characters & countries
Law & Legal Topics
Linguistics
Movies
Most successful Movies
Science Plus
Science & Computers
Quantum Theory
|