A metallic conductor at `10^(@)C` connected in the left gap of meter bridge gives balancing length 40 cm. When the conductor is at `60^(@)C`, the balancing point shifts by --- cm, (temperature coefficient of resistance of the material of the wire is `((1)/(220))/(.^(@)C))`

Options

A. 4.8
B. 10
C. 15
D. 7

Answer

A

Explanation

`(X)/(R)=(40)/(60)=(2)/(3),(X_(0)(1+alphat_(1)))/(R)=(2)/(3)`
`(X_(0)(1+alphat_(2)))/(R)=(l)/(100-l)`
`(1+alphat_(1))/(1+alphat_(2))=(2)/(3)xx[(100-l)/(l)]`
`l=44.8`
Balancing point shift by `=44.8-40=4.8`