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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 ...
When this is the case, the resistance of the conductor is directly proportional to its length and inversely proportional to its cross-sectional area, where the electrical resistivity ρ (Greek: rho) is the constant of proportionality. This is written as:
Ohm's law states that the electric current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, [1] one arrives at the three mathematical equations used to describe this relationship: [2]
Also, for a given material, the resistance is proportional to the length; for example, a long copper wire has higher resistance than an otherwise-identical short copper wire. The resistance R and conductance G of a conductor of uniform cross section, therefore, can be computed as [1]
The inverse of the resistance is known as the conductance. When we consider a metal of unit length and unit cross sectional area, the conductance is known as the conductivity, which is the inverse of resistivity. The Drude model attempts to explain the resistivity of a conductor in terms of the scattering of electrons (the carriers of ...
Portal:Electronics/Selected article/1 . Ohm's law states that, in an electrical circuit, the current passing through a conductor, from one terminal point to another, is directly proportional to the potential difference (i.e. voltage drop or voltage) across the two terminal points and inversely proportional to the resistance of the conductor between the two terminal points.
As the length of an antenna is made shorter than its fundamental resonant length (a half-wavelength for a dipole antenna and a quarter-wavelength for a monopole), the radiation resistance the antenna presents to the feedline decreases with the square of the electrical length, that is the ratio of physical length to wavelength, (/). As a result ...
Ohm's law states that the voltage across a resistor is proportional to the current passing through it, where the constant of proportionality is the resistance (). For example, if a 300- ohm resistor is attached across the terminals of a 12-volt battery, then a current of 12 / 300 = 0.04 amperes flows through that resistor.