Low of resistance

LOW OF RESISTANCE

Low of Resistance:-

• Low of resistance is also called geometrical definition of resistance.
• It is also called geometrical definition of ohms low.
• The resistance of a conductor is directly proportional to the length  of a conductor.

             

• The resistance of a conductor is inversely proportional to the cross section area  of a conductor. 

           

• Resistance of conductor depend on temperature.
• Resistance of conductor depend on nature of substance or internal structure of a substance. 
• from equation (i) &(ii)

         

• Resistivity:-
• Unit length and unit cross section area of conductor abstract the current, this property is called resistivity.
• Resistivity is just like a molecular resistance of substance.
• SI-Unit of resistivity is "ohm meter".

• Dependency of Resistivity:-
• It is not depend on length of a conductor.
• It is not depend on cross section area of a conductor.
• It is depend on nature of substance or internal structure of a substance. 
• It is depend on temperature.
• In conductor, resistivity is positive temperature cofficiant.(PTC)
• In conductor, temperature will be increased than resistivity will be increased(vice versa).
•  In semi conductor, resistivity is negative  temperature cofficiant.(NTC )
• In semi conductor, temperature will be increased than resistivity will be decrease (vice versa).
• In insulator, resistivity is positive temperature cofficiant.(PTC)
• In insulator, temperature will be increased than resistivity will be increased(vice versa).

• Dependency of Resistance:-
• It is depend on length of a conductor.
• If length will be increased than resistance will be increased(vice versa)
• It is  depend on cross section area of a conductor.
• If cross section area will be increased than resistance will be decrease(vice versa)
• It is depend on nature of substance or internal structure of a substance. 
• It is depend on temperature.
• In conductor, resistance is positive temperature cofficiant.(PTC)
• In conductor, temperature will be increased than resistance will be increased(vice versa).
•  In semi conductor, resistance is negative  temperature cofficiant.(NTC )
• In semi conductor, temperature will be increased than resistance will be decrease (vice versa).
• In insulator, resistance is positive temperature cofficiant.(PTC)
• In insulator, temperature will be increased than resistance will be increased(vice versa)