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For a given material, the resistance is inversely proportional to the cross-sectional area; for example, a thick copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a given material, the resistance is proportional to the length; for example, a long copper wire has higher resistance than an otherwise ...
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]
The resistance of a given element is proportional to the length, but inversely proportional to the cross-sectional area. For example, if A = 1 m 2 , ℓ {\displaystyle \ell } = 1 m (forming a cube with perfectly conductive contacts on opposite faces), then the resistance of this element in ohms is numerically equal to the resistivity of the ...
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.
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 ]
Resistance R is proportional to the distance l between the electrodes and is inversely proportional to the cross-sectional area of the sample A (noted S on the figure above). Writing ρ (rho) for the specific resistance, or resistivity ,
It follows that the resistance R is proportional to the length L of the resistor, which is true. However, it also follows that the resistance R is inversely proportional to the fourth power of the radius r , i.e. the resistance R is inversely proportional to the second power of the cross section area S = π r 2 of the resistor, which is ...
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 ...