Question

what is the factional change in the resistance of an iron filament when its temperature changes from 25 to 50 degrees celcius?

Answer 1

The temperature dependence of resistance is given by equation

$$R(t_2)=R(t_1)(1+\alpha (t_2-t_1)).$$

The fractional change in the resistance

$$\frac{R(t_2)-R(t_1)}{R(t_1)}=\alpha (t_2-t_1)\\ =0.00651\times (50-25)=0.16.$$