1) A piece of wire with resistance R is stretched to anadditional 20% on its ori

Question

1) A piece of wire with resistance R is stretched to anadditional 20% on its original length. Assuming volume doesnot change, what is he relation of new resistance to theoriginal R?
2) A copper wire and a iron wire have the same diameter,length and carry the same current. In which wire is thepotential difference greater? pCu = 1.7 x 10-8ohmmeters and pFe= 1.0 x 10-8ohm meters 3) How does the E fields in Cu and Fe compare? 1) A piece of wire with resistance R is stretched to anadditional 20% on its original length. Assuming volume doesnot change, what is he relation of new resistance to theoriginal R?
2) A copper wire and a iron wire have the same diameter,length and carry the same current. In which wire is thepotential difference greater? pCu = 1.7 x 10-8ohmmeters and pFe= 1.0 x 10-8ohm meters 3) How does the E fields in Cu and Fe compare?

Explanation / Answer

Resistance of original wire R = R

Length of original wire L = L

Area of cross section of original wire A = A

New length L ‘ = L + 20 % L = 1.2 L

Volume remains constant .i.e., AL= A’L’

From this new area of crosssection A ‘ = AL / L’

                                                              = A/ 1.2

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