Question

Question #22725

Answer 1

`8Omega`

Explanation:

Resistance `R_T` of a metallic wire is expressed in terms of its temperature `T`, stated in `"^@`C, as

`R_T=R_"ref"[1+alpha(T-T_"ref")]` ....(1)
where `R_"ref"` is resistance at reference temperature `T_"ref"`, usually `20^@"C".` Sometimes `0^@"C"` and
`alpha` is temperature coefficient of the conductor material.
Let us assume `T_"ref"` be `0^@"C"`, from (1) we obtain
`R_0=5Omega`
To calculate `alpha` we use given resistance at `100^@"C"`. Again from (1)
`7=5[1+alpha(100-0]`
`=>alpha=(7/5-1)/100`
`=>alpha=(2)/500`
`=>alpha=0.004`

To calculate resistance at `150^@"C"`, again from (1)
`R_150=5[1+0.004(150-0)]`
`R_150=8Omega`