1. calculate the resistance of a copper wire 1.0km long and 0.50 mm diameter if the resistivity of copper is 1.7 x 10( 10 to the power -8 ) ?? 2. The resistance of a metal wire of length 1m is 26 ohms at 20 'c .If the diameter of the wire is 0.3mm, what will be the resistivity of the metal at that temperature ????

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2015-12-09T14:56:40+05:30

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1.       Length, L = 1000 meter
         Diameter, D = 0.50 mm, r = 0.25 mm = .25X10(-3) meter

         Sp Resistance, ρ = 1.7 X 10(-8)                  
           ρL        1.7 X 10(-8) X 1000
 
R  =   ---   =  --------------------------  =  85 ohm
            
           A      
      .25X10(-3)    


2.     
Length, L = 1 meter

         Diameter, D = 0.30 mm, r = 0.15 mm = .15X10(-3) meter
   
         Resistance, R = 26 ohm
       
         Ρ = (RA)/L
            
             = (RX πr2 )/L = (26X3.14X0.15X0.15)/ (1X103X103)          
             = 1.84 X 10(-6) Ωm

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