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where is the length of the conductor, measured in metres [m], A is the cross-section area of the conductor measured in square metres [m 2], σ is the electrical conductivity measured in siemens per meter (S·m −1), and ρ is the electrical resistivity (also called specific electrical resistance) of the material, measured in ohm-metres (Ω·m ...
Also called chordal or DC resistance This corresponds to the usual definition of resistance; the voltage divided by the current R s t a t i c = V I. {\displaystyle R_{\mathrm {static} }={V \over I}.} It is the slope of the line (chord) from the origin through the point on the curve. Static resistance determines the power dissipation in an electrical component. Points on the current–voltage ...
The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In normal (that is, non-superconducting) conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the ...
In conductors where the charge carriers are positive, conventional current is in the same direction as the charge carriers. In a vacuum , a beam of ions or electrons may be formed. In other conductive materials, the electric current is due to the flow of both positively and negatively charged particles at the same time.
Proton conductors are electrolytic conductors employing positive hydrogen ions as carriers. [8] In a plasma, an electrically charged gas which is found in electric arcs through air, neon signs, and the sun and stars, the electrons and cations of ionized gas act as charge carriers. [9] In a vacuum, free electrons can act as charge carriers.
Electronic band theory (a branch of physics) explains that electric charge flows when quantum states of matter are available into which electrons can be excited. This allows electrons to gain energy and thereby move through a conductor, such as a metal, if an electric potential difference is applied to the material. If no such states are ...
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.
The electrical resistance of a uniform conductor is given in terms of resistivity by: [40] = where ℓ is the length of the conductor in SI units of meters, a is the cross-sectional area (for a round wire a = πr 2 if r is radius) in units of meters squared, and ρ is the resistivity in units of ohm·meters.