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In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. [1] The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.
Conductors installed so that air can freely move over them can be rated to carry more current than conductors run inside a conduit or buried underground. High ambient temperature may reduce the current rating of a conductor. Cables run in wet or oily locations may carry a lower temperature rating than in a dry installation. A lower rating will ...
L −2 M −1 T 3 I 2: scalar Electrical conductivity: σ: Measure of a material's ability to conduct an electric current S/m L −3 M −1 T 3 I 2: scalar Electric potential: φ: Energy required to move a unit charge through an electric field from a reference point volt (V = J/C) L 2 M T −3 I −1: extensive, scalar Electrical resistance: R
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 ...
The resistivity can be expressed using the SI unit ohm metre (Ω⋅m) — i.e. ohms multiplied by square metres (for the cross-sectional area) then divided by metres (for the length). Both resistance and resistivity describe how difficult it is to make electrical current flow through a material, but unlike resistance, resistivity is an ...
≈ 404.6873 m 2: square foot: sq ft ≡ 1 ft × 1 ft: ≡ 9.290 304 × 10 −2 m 2: square foot (US Survey) sq ft ≡ 1 ft (US) × 1 ft (US) ≈ 9.290 341 161 3275 × 10 −2 m 2: square inch: sq in ≡ 1 in × 1 in: ≡ 6.4516 × 10 −4 m 2: square kilometre: km 2: ≡ 1 km × 1 km = 10 6 m 2: square link (Gunter's)(International) sq lnk ≡ ...
where is the length of the conductor, measured in metres (m), A is the cross-sectional 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 ...
MC3 is the abbreviation of Multi-Contact and its size 3mm PV connector with 3 mm contact pin. MC3 had certification ratings of (1000VIEC/600V UL) and 30A (10AWG PV Cable). The MC3 connectors were discontinued in 2016. MC4 name stood for Multi-Contact and its size 4mm PV connectors, introduced by Multi-Contact in 2004.