A compound bar consists of two sections of different materials, having coefficients of nonlinear expansion `alpha_(1) and alpha_(2)` respectively. The length of section-I is a fraction `f_1` of the total and length and length of section-2 is fraction `f_2` of the total length. The effective coefficient of linear expansion of the composite bar is

Options

A. `alpha= f_(1) alpha_(2) + f_(2) alpha_(1)`
B. `alpha= f_(1) alpha_(1) + f_(2) alpha_(2)`
C. `alpha= f_(1) alpha_(2) - f_(2) alpha_(1)`
D. `alpha= f_(1) alpha_(1) - f_(2) alpha_(2)`

Answer

B