Physics Past Paper PDF - Differences Based on Resistivity and Conductivity

Differences Based on Resistivity and Conductivity (i) Metals: They possess very low resistivity (or high conductivity). 𝜌 ∼ 10−2 − 10−8Ω m 𝜎 ∼ 102 − 108Sm−1 (ii) Semiconductors: They have resistivity or conductivity intermediate to metals and insulators. 𝜌 ∼ 10−5 − 106Ω m 𝜎 ∼ 10...

Differences Based on Resistivity and Conductivity (i) Metals: They possess very low resistivity (or high conductivity). 𝜌 ∼ 10−2 − 10−8Ω m 𝜎 ∼ 102 − 108Sm−1 (ii) Semiconductors: They have resistivity or conductivity intermediate to metals and insulators. 𝜌 ∼ 10−5 − 106Ω m 𝜎 ∼ 105 − 10−6 S m−1 (iii)Insulators: They have high resistivity (or low conductivity). 𝜌 ∼ 1011 − 1019Ω m 𝜎 ∼ 10−11 − 10−19Sm−1  Correct order of relative values of electrical conductivity σ for different types of solid is (a) semiconductor > insulator > metal σ σ σ (b) metal > semiconductor σ σ σ > insulator (c) semiconductor > metal > σ σ σinsulator (d) insulator > semiconductor σ σ σ > metal 6 ✓Valence band : range of energies possessed by valence electrons in a crystal ✓Contains valence electrons ✓Valence band electrons do not participate in electrical conductivity. ✓Conduction band: the band above the valence band ✓Range of energies possessed by free electrons ✓Electrons may or may not exist here. ✓These electrons are responsible for electrical conductivity  Energy Gap ✓ Electrons in VB may gain energy and jump to CB. ✓ Electrons can’t exist in EG ✓ Some energy levels in between VB & CB are forbidden (restricted, prohibited) for electrons. ✓ These energy levels are together known as FEG  (a) What is meant by forbidden energy gap? [MODEL 2021] 10