Chapter-3|Current Electricity| NCERT 12th Physics:
Effect of Temperature on Resistance:
Experimentally it was observed that on increasing temperature from T to T+dT, Resistance changes from R₀ to R₀+dR, then
For metals the value of α is positive, therefore resistance of the metal increases with rise in temperature. For insulators and semiconductors the value of α is negative, therefore resistance decreases with rise in temperature.