Equal lengths of wires A and B are connected the left and the right gap respectively of a meter bridge. The null point is obtained at 0.4 m from the left end of the wire. If the diameters of the wires A and B are in the ratio 2:3 . Then the ratio of specific resistances of the materials of the wires will be

Options

A. `8:27`
B. `8:15`
C. `27:8`
D. `15:8`

Answer

A

Explanation

`(R_(1))/(R_(2))=(l_(x))/(l_(r))`
`:.(rho_(1))/(rho_(2))xx(l_(1))/(l_(2))xx(A_(2))/(A_(1))=(l_(x))/(l_(r))`
`:.(rho_(1))/(rho_(2))=(l_(2))/(l_(1))xx(r_(1)^(2))/(r_(2)^(2))`
`=4/9xx4/6=8.27`