1.

Equal lengths of manganin wire and constantan wire, of equal cross-sectional areas, are connected respectively in the left gap and right gap of a Wheatstone bridge which has a wire 90 cm long. If the null point is obtained at 44 cm from the left end, the ratio of the conductivity of manganin to that of constantan is

Answer»

`(11)/(14)`
`(14)/(11)`
`(22)/(23)`
`(23)/(22)`

Solution :`(R_(M))/(R_(C))=(rho_(M))/(rho_(C))=(sigma_(C))/(sigma_(M))(because " L and A are the same, and "sigma=(1)/(rho))`
`"Also, "(R_(M))/(R_(C))=(l_(M))/(l_(C))=(44)/(90-44)=(44)/(46)=(22)/(23)`
`therefore (sigma_(M))/(sigma_(C))=(R_(C))/(R_(M))=(23)/(22)`


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