# Electrical Resistance of Metals But, why is it so?

## Electrical Resistance of Ferromagnetic Metals | Progress of Theoretical Physics | Oxford Academic

It is because of a phenomenon that we will read about in this chapter. We will study about resistivity of various materials. We know that electric current that flows in a circuit is as similar to the water flowing through a river. In a river rock, branches and other particles resist the flow of water. Resistance is nothing but this property of resisting the flow of electrons or the current. The unit of resistance is ohm.

One ohm is equal to volt per ampere. Resistors are used to resist or control the flow of electrons by the conductive material. They do not provide any power to the circuit. They may reduce the voltage and current passing through the circuit. Hence, resistors are passive devices.

Resistivity or specific resistance of a material - in Hindi - हिंदी

Most of the resistors are made up of carbon , metal or metal oxide film. Resistivity is the resistance per unit length and cross-sectional area. It is the property of the material that opposes the flow of charge or the flow of electric current. The unit of resistivity is ohm meter.

Thus we can derive the expression for resistivity from this formula. When the values of L, the length , and A, the area is equal to one, we can say that the resistivity is equal to the resistance. So, resistivity is the specific resistance of a material.

When we have a thick wire, the resistance decreases. In most cases, these bands overlap each other. The valence electrons in a given atom are loosely bound to the nucleus in a conducting material. Quite often, metals or conductors have a low ionization energy and therefore, they tend to lose electrons very fluidly. When an electric current is applied, the electrons are free to move within the structure on their own. This happens in the case of the normal temperature of a material.

### Contrasting student and scientific views

However, when the temperature increases gradually, the vibrations in the metal ions in the lattice structure also undergo an increase. In this case, the atoms begin to vibrate with a higher amplitude. Such vibrations, in turn, cause frequent collisions between the free electrons and the remaining electrons.

Each such collision drains out some degree of energy of the free moving electrons and renders them in a condition in which they are not able to move. Thus, it causes a restriction in the movement of the delocalized electrons. In the case of metals or conductors, it is rightly said that they hold a positive temperature coefficient.

### What is Resistance?

For most of the metals, the resistivity increases in a linear pattern with an increase in the temperature in a range of K. In the case of insulators, the forbidden energy gap between the conduction band and the valence band is very high.

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The valence band is filled with the electrons of the atoms. Diamond is a unique example of an insulator. Here, all the valence electrons are involved in the covalent bond formation and as a result, conduction does not take place. Resistors are used to resist or control the flow of electrons by the conductive material. They do not provide any power to the circuit. They may reduce the voltage and current passing through the circuit.

## Metal properties table

Hence, resistors are passive devices. Most of the resistors are made up of carbon , metal or metal oxide film. Resistivity is the resistance per unit length and cross-sectional area. It is the property of the material that opposes the flow of charge or the flow of electric current. The unit of resistivity is ohm meter.

Thus we can derive the expression for resistivity from this formula. When the values of L, the length , and A, the area is equal to one, we can say that the resistivity is equal to the resistance. So, resistivity is the specific resistance of a material. When we have a thick wire, the resistance decreases. The resistance increases when the wire is thin as the area of cross-section is less.

When the length of the wire increases, the resistance also increases. When the length of the wire decreases, the resistance decreases as the length is less. A material with high resistivity means it has got high resistance and will resist the flow of electrons. A material with low resistivity means it has low resistance and thus the electrons flow smoothly through the material. For example, Copper and Aluminium have low resistivity. Good conductors have less resistivity.

Insulators have a high resistivity. Electrical Resistance of Metals Electrical Resistance of Metals Electrical Resistance of Metals Electrical Resistance of Metals Electrical Resistance of Metals Electrical Resistance of Metals Electrical Resistance of Metals

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