1.

A copper wire and an iron wire, each having an area of cross-section A and lengths L_(1) and L_(2) are joined end to end. The copper end is maintained at a potential V_(1) and the iron end at a lower potential V_(2). If sigma_(1) and sigma_(2) are the conductivities of copper and iron respectively, then the potential of the junction will be

Answer»

`(sigma_(1)V_(1)+sigma_(2)V_(2))/((sigma_(1)//L_(1))+(sigma_(1)//L_(2)))`
`((sigma_(1)V_(1))/(L_(1))+(sigma_(2)V_(2))/(L_(2)))/((sigma_(1)//L_(1))+(sigma_(1)//L_(2)))`
`((sigma_(1)//V_(1))+(sigma_(2)//V_(2)))/(sigma_(1)V_(1)+sigma_(2)V_(2))`
`(sigma_(1)V_(1)-sigma_(2)V_(2))/((sigma_(1)//L_(1))-(sigma_(1)//L_(2)))`

ANSWER :B


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