Resistivity is a physical constant, and is unaffected by the dimensions of the wire. In simpler models non quantum mechanical models this can be explained by replacing electrons and the crystal lattice by a wave-like structure. Superconductivity The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered.
In biological membranescurrents are carried by ionic salts. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source. However, due to the sheer number of moving electrons, even a slow drift velocity results in a large current density.
No, a thicker wire has less resistance. Electric current consists of a flow of electrons. However, the resistance decreases as the charge carrier density i.
The resulting resistance of the parallel combination will be the resistance of the original wire divided by n squared. In metals there are many electron energy levels near the Fermi level, so there are many electrons available to move.
Resistance for a given material and length is basically proportional to the cross-sectional area of a wire. The more regular the lattice is, the less disturbance happens and thus the less resistance.
In insulators and semiconductors the Fermi level is inside a band gap ; however, in semiconductors the bands are near enough to the Fermi level to be thermally populated with electrons or holes. Hence, highly doped semiconductors behave metallically.
Causes of conductivity[ edit ] See also: The thin wire has more resistance to the flow of electric current than the thick wire. In general though a stranded wire of the same composition as a solid wire does not have more resistance.
Since there are no available states near the Fermi level, and the electrons are not freely movable, the electronic conductivity is very low. A wire long thin - often cylindrical rod that is mad of a reddish metal and which conducts electricity and heat very well.
This is also known as a positive ionic lattice. The characteristic energy level up to which the electrons have filled is called the Fermi level.
Most metals have electrical resistance. A "hole" is a position where an electron is missing; such holes can behave in a similar way to electrons. Copper wire has the best conductivity, for the price, of any metal.
Here, height is energy while width is the density of available states for a certain energy in the material listed. When an electrical potential difference a voltage is applied across the metal, the resulting electric field causes electrons to drift towards the positive terminal.
For both types of donor or acceptor atoms, increasing dopant density reduces resistance. Does a thicker wire equal more resistance? Second, the purity of the metal is relevant as a mixture of different ions is also an irregularity. Small holes in cell membranes, called ion channelsare selective to specific ions and determine the membrane resistance.
So the electrons "fill up" the band structure starting from the bottom. Band theory Filling of the electronic states in various types of materials at equilibrium. Does a long wire have more resistance than a short wire?
Why does a short wire have less resistance And a long wire have more resistance? The resistivity of ionic solutions electrolytes varies tremendously with concentration — while distilled water is almost an insulator, salt water is a reasonable electrical conductor.
Does the length of copper wire affects its resistivity? The amount of resistance is thus mainly caused by two factors. The position of the Fermi level with respect to the band structure is very important for electrical conduction: However, as you point out different wire materials exhibit different resistances for equal sizes silver conducts better than copper, etc.
These are used in biology to transfer microorganisms to culture media, and in chemistry to do flame tests.Feb 05, · ICSE physics question: why is a heater element preferably made of nichrome and not copper? i've thought of two possible answers: ONE: since nichrome has a higher resistivity than copper, so the higher resistance makes nichrome produce heat more readily than copper when current flows through ultimedescente.com: Resolved.
First copper is an element and nichrome is an alloy primarily of nickel,chromium and iron. So that's the first clue noting that the three elements that make up this alloy have a smaller conductivity than copper.
But there's more to the reason for higher resistance. The voltage is the "push" on the electrons, and their flow is the current. If you have a nichrome wire and a copper wire the same size and shape, with the same voltage on them, much more current will flow through the copper.
We say that the copper has higher 'conductivity' or lower 'resistivity'. Nichrome has over 65 times the resistance of an equal piece of copper. If a piece of copper and nichrome wires have the same resistance the copper wire will be thinner and/or longer.
Nichrome is composes of about 80% nickle and 20% chromium. Both constituents have a much higher resistivity than copper. Nichrome wire has such high resistance that it is used to convert electrical energy into heat. Many heating elements are made from nichrome.
Copper wire has the best conductivity, for the price, of any metal. For example, rubber has a far larger resistivity than copper. In a hydraulic analogy, passing current through a high-resistivity material is like pushing water through a pipe full of sand—while passing current through a low-resistivity material is like pushing water through an empty pipe.Download