The temperature coefficient of resistance of a material is given as :

Temperature coefficient of resistance

It is the calculation of a relative change of resistance per degree of temperature change.

The value of the resistance at temperature 't₂' is given by:

\(R_t=R_o[1+α (t_2-t_1)]\)

where, R_t = Final resistance at temperature 't₂'

R_o = Initial resistance at temperature 't₁'

α = Temperature coefficient of resistance

The value of α is calculated as:

\({R_t\over R_o}=1+α (t_2-t_1)\)

\({R_t\over R_o}-1=α (t_2-t_1)\)

\({R_t-R_o\over R_o}=α (t_2-t_1)\)

\(α ={R_t-R_o\over R_o(t_2-t_1)}\)

Hence, the correct answer is option 4.