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Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge.Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations.
In electromagnetism, Jefimenko's equations (named after Oleg D. Jefimenko) give the electric field and magnetic field due to a distribution of electric charges and electric current in space, that takes into account the propagation delay (retarded time) of the fields due to the finite speed of light and relativistic effects.
The current entering any junction is equal to the current leaving that junction. i 2 + i 3 = i 1 + i 4. This law, also called Kirchhoff's first law, or Kirchhoff's junction rule, states that, for any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node; or equivalently:
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
For example, in a copper wire of cross-section 0.5 mm 2, carrying a current of 5 A, the drift velocity of the electrons is on the order of a millimetre per second. To take a different example, in the near-vacuum inside a cathode-ray tube , the electrons travel in near-straight lines at about a tenth of the speed of light .
Ohm's Law chapter from Lessons In Electric Circuits Vol 1 DC book and series. John C. Shedd and Mayo D. Hershey, "The History of Ohm's Law" , Popular Science , December 1913, pp. 599–614, Bonnier Corporation ISSN 0161-7370 , gives the history of Ohm's investigations, prior work, Ohm's false equation in the first paper, illustration of Ohm's ...
Induction: Faraday's law and Lenz's law – Highly animated lecture, with sound effects, Electricity and Magnetism course page; Notes from Physics and Astronomy HyperPhysics at Georgia State University; Tankersley and Mosca: Introducing Faraday's law; A free simulation on motional emf
Alternator – Device converting mechanical into electrical energy; Crosstalk – Signals in one channel affecting another; Faraday paradox – Apparent paradox with Faraday's law of induction; Fleming's right-hand rule – Mnemonic for the direction of induced current in a moving magnetic field; Hall effect – Electromagnetic effect in physics