Ohm's law
Ohm's law
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Ohm's law says that electric current through a conductor between 2 points is directly proportional to a voltage across the 2 points, like in a electric circuit.
Introducing constant of proportionality, the resistance, one arrives at the three mathematical equations used to describe this relationship:
V = voltage
I = current
R = resistance
In other words, Ohm's law says that R here is constant, independent of the current.
If the resistance is inconstant, the previous equation isn't Ohm's law, but it can still be used as a definition of static/DC resistance.
The law is an empirical relation that accurately describes the conductivity of most electrically conductive materials over orders of current magnitudes.
empirical: based on, concerned with, observed
Materials not obeying Ohm's law are called non-ohmic.
Ohm's law is named after German mathematician and physicist Georg Simon Ohm.
In physics, Ohm's law also refers to many generalizations of the law;
E.g. the law's vector form in electromagnetics and material science:
It's an Ohm's law reformulation is due to Gustav Kirchhoff.
J = current density at a resisitve material's location
E = location's electric field
σ (sigma) = material-dependent parameter called conductivity, defined as the inverse of resistivity ρ (rho)
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