Consider four conducing materials copper, tungsten, mercury and aluminum with resistivity ${\mathrm{\rho }}_{\mathrm{C}}, {\mathrm{\rho }}_{\mathrm{T}}, {\mathrm{\rho }}_{\mathrm{M}}$ and ${\mathrm{\rho }}_{\mathrm{A}}$ respectively. Then :

Assertion :- The value of temperature coefficient of resistance is positive for metals.

Reason :- The value of temperature coefficient of resistance is negative for insulators.