Saturday, August 25, 2012



          In this post, we will learn about the resistance and the resistivity of a conductor . In our 1st post about direct current, we studied about the current flowing through a battery. To carry the current we need a media. that media is a conductor. Metals , acids, and salt solutions are good conductors of electricity. Here we study about metal conductors. 

                                 This resistance to the flow of electrons occurs due to the electric friction . Just keep in mind that this friction is very similar to the friction in mechanics. Resistance is offered by 'R' .

The resistance of a conductor not only depends on the metal type. Consider two different conductors which are made of the same metal, the resistance of those may not be same. There are three factors affects on the resistance of a conductor
  1. Length of the conductor
  2. Cross sectional area of the conductor ( area normal to the current)
  3. Metal type (resistivity or the specific resistance )
resistivity is offered by the greek letter 

 Figure 2.1

When a road gets narrowed, traffic goes higher. similar to that, when the cross section is small,then the resistance  goes higher . So the cross sectional area is inversely proportion to the resistance. And when the road length is large, number of barriers we face increase. Similar to that , resistance increases with the length of the conductor. So length of the conductor is directly proportional to the resistance. The proportion constant is the resistivity of the metal.

In our next post, we will discuss about the Ohm's law.

pabindu lakshitha (engineering undergraduate )

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