Effect of temperature on Resistance

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We know that there are some materials whose resistance remains same and they offer same resistance for the flow of current despite of increasing the applied voltage.

Those materials whose resistance remains same and provide same resistance for the flow of current and the flow of current increases with the increase in applied voltage are called Ohmic materials.

Some examples of such materials are Copper, Silver, Nichrome, Manganin, Constantan etc.

 

But for some materials including conductors and insulators, the resistance does not remains same by positive or negative change in temperature and in this article, we will explain and exemplify such materials.

1.       Effect of temperature on conductors:

  Conductors are those materials which have the availability of free electrons and because of the availability of the free electrons they can conduct electricity from one point to another.                                                 

In the given figure, we have a conductor of a cross sectional area A and length L and there are atoms inside it which are vibrating around there mean point. When the temperature of the conductor increases by any means, let because of the heating effect of the current, then the vibrations of the atoms become more rapid and violent and they collide with each other more frequently them before. These collisions create more hindrance to the flow of electrons and thus the resistance increases with increase in temperature in such materials.

Example:

Tungsten filament is a good example of a material whose resistance increases with the increase in temperature.

1.    2..    Effect of temperature on non-conductors or Semi-conductors:

                                                                                                                     Nonconductors are those materials which do not have the availability of the free electrons. This means that all the electrons available around the atoms (including the valence shell electrons) are bonded with the nucleus thus they are unable to move freely 

If these bonded electrons get enough energy from any source then they absorb that energy and after a certain interval of Time, their energy becomes so higher that they leave the valence shell and becomes a free electrons. This energy can be Available for the electrons from the heating effect produced by the current. Hence these newly formed free electrons starts to conduct heat and thus we conclude the solution that by increasing the Temperature, the resistance of the Non-conducting materials decreases and they start conducting the current.

Example:

                   Thermistor, also called a temperature dependent resistor is a good example of a material whose resistance decreases with the increase in temperature.

 

we will discuss about the temperature coefficient of resistance and resistivity in the next blog.

write a comment if you face any problem understanding the above concept.