A fine steel wire of length `4`m is fixed rigidly in a heavy brass frame as ashown in figure . It is just taut at `20^(@)C`. The tensile stress developed in steel wire it whole system is heated to `120^(@)C` is :-
(`Given alpha _("brass") = 1.8 xx 10^(-5) .^(@)C^(-1), alpha_("steel") = 1.2 xx 10^(-5) .^(@)C, Y_("steel") = 2 xx 10^(11) Nm^(-2), Y_("brass")= 1.7xx10^(7) Nm^(-2)`)

Options

A. `1.02 xx 10^(4) Nm^(-2)`
B. `1.2 xx 10^(8) Nm^(-2)`
C. `1.2 xx 10^(6) Nm^(-2)`
D. `6 xx 10^(8) Nm^(-2)`

Answer

B

Explanation

Stress = `Y` (strain) = `Y_(S)(alpha_(b)-alpha_(s))DeltaT= (2xx10^(11)) (0.6xx10^(-5)) (100) = 1.2 xx 10^(8) Nm^(-2)`