A copper wire of conductance 72 Ω-1 is melted and redrawn to thrice its original length. Find the Conductance of stretched wire.

  • Option 1)

    6 Ω-1

  • Option 2)

    8 Ω-1

  • Option 3)

    9 Ω-1

  • Option 4)

    12 Ω-1

 

Answers (1)
P Plabita

As we learnt

 

Conductance -

 

C=\frac{1}{R}

C=  Conductance

- wherein

 

 

Since volume of the wire does not change.

Þ l1A1 = l2 A2  where l­1­  and A1 are the initial length and cross-section of the wire, and l2 and A2 are the final length and cross-section.

        Þ           \frac{{{l_1}}}{{{l_2}}} = \frac{{{A_2}}}{{{A_1}}}$              

 

C1 = A1/ρL1   and     C2 = A2/ ρ L1

                        Þ           C1/C2 = L22/L21    = 9

 

Þ C2= C1/9 = 8 Ω-1


Option 1)

6 Ω-1

Option 2)

8 Ω-1

Option 3)

9 Ω-1

Option 4)

12 Ω-1

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