Thursday, 14 February 2013

OHM'S LAW


Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance one arrives at the usual mathematical equation that describes this relationship:
                                                      V = I R
                                                   
                                                      I = V / R


In physics, the term Ohm's law is also used to refer to various generalizations of the law originally formulated by Ohm. The simplest example of this is:
                                                    
                                                       J = σ E
IMPORTANT POINTS

1) Ohms law is applicable to linear passive bilateral circuits (At const. temp) 

2) it is not applicable to active elements

3) it depends on nature of elements

4) Ohm's Law doesn't apply to many semiconducting devices, because they are not linear or ohmic -that is the ration of voltage to current doesn't remain constant for changes in voltage. Semiconducting devices, such as diodes, are termed 'non-linear' or 'non-ohmic' because their ratio of voltage to current changes whenever the applied voltage changes.

5) Ohms law is applicable only for Elements but not Sources.

6) Ohm's law is applicable only Lumped elements

7) Ohm's Law is applicable only When Temparature is kept constant.

8)   Ohm's law is applicable for Field Theory


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