With the rise of temperature, the conductivity of a semi-conductor:

CONCEPT:

• Semiconductors: The materials that have a conductivity between conductors and insulators are called semiconductors.
• Conductivity (k) is the measure of the ease at which an electric charge or heat can pass through a material.
• Resistivity (ρ): Resistivity is the resistance per unit length and cross-sectional area
  • It is the property of the material that opposes the flow of charge or the flow of electric current
• The relation between conductivity and resistivity is given by

⇒ ρ = 1/k

EXPLANATION:

• The electrical conductivity of a semiconductor increases with a rise in temperature and such semiconductors have a negative temperature coefficient of resistance.
• The conductivity of the semiconductor is inversely proportional to the resistivity of the material.
• As the temperature increases, the resistivity decreases, and hence the conductivity of semiconductors increases. Therefore option 1 is correct.

Additional Information

• In Metals: As the temperature increases, the carrier concentration remains almost the same, but there is a decrease in mobility due to lattice scattering or the frequency of collision increases and hence resistance also increases.
  • So that conductivity decreases & resistivity increases, which implies the temperature coefficient of resistivity for metals is positive.