Why do materials have electrical resistance

The following are the various materials used to make resistors. Manganin: Manganin is an alloy of Copper, Manganese and Nickel.

It has high resistivity nearly 25 times that of the copper. Nickel Chromium Alloy: This alloy has a higher temperature coefficient of resistivity than Manganin and Constantan. The most important property of this alloy is that it remains stable and corrosion resistant even at a higher temperature.

This alloy has resistivity about 20 times that of Copper. Resistance Box. The resistance of a conductor is said to be 1 ohm, if a current of 1 A flows through it when potential difference of 1 V is applied across it. What is the dimensional formula of resistance?

The dimensional formula of resistance is [ML 2 T -3 A -2 ]. This site uses Akismet to reduce spam. Learn how your comment data is processed. We've detected that you are using AdBlock Plus or some other adblocking software which is preventing the page from fully loading. The shape and size of the particular metal also influences its level of resistance to electrical flow.

Metals are good conductors of electricity. Electrons in atoms hold atoms together in a crystal structure. When electrons move up to the surface of a material, they move freely to conduct electricity when a charge is applied to the substance. In metal, electrons move readily from the valence band, where they usually reside, to the conduction band, where they are free to move through the material. There are so few free electrons that hardly any current can flow.

Almost all the electrons are tightly bound within their particular atom. Heating an insulating material vibrates the atoms, and if heated sufficiently, the atoms vibrate violently enough to actually shake some of their captive electrons free, creating free electrons to become carriers of current.

Therefore at high temperatures the resistance of an insulator can fall, and in some insulating materials, quite dramatically. Different materials within either group have different temperature coefficients.

Materials chosen for the construction of the resistors used in electronic circuits are carefully selected conductors that have a very low positive temperatur coefficient. In use, resistors made from such materials will have only very slight increases in resistivity, and therefore their resistance. Using such materials for the manufacture of resistors creates components whose value changes only slightly over a given range of temperature.

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