Resistivity values classify materials as conductors, semiconductors, or insulators

Resistivity & Superconductivity — AQA A-Level Physics

Metals have very low resistivityA material property that quantifies how strongly it resists currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A).. Measured in ohm-metres (Ω m).: copper ≈ 1.7 × 10⁻⁸ Ω m, gold ≈ 2.4 × 10⁻⁸ Ω m, aluminium ≈ 2.6 × 10⁻⁸ Ω m.
SemiconductorsMaterials with resistivityA material property that quantifies how strongly it resists currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A).. Measured in ohm-metres (Ω m). between conductors and insulators. Their number densityMass per unit volume of a material. Measured in kg m⁻³. of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). carriers increases with temperature. have intermediate resistivityA material property that quantifies how strongly it resists currentThe rate of flow of charge. Measured in amperes (A).. Measured in ohm-metres (Ω m).: germanium ≈ 0.6 Ω m, silicon ≈ 2.3 × 10³ Ω m.
Insulators have extremely high resistivity: glass ≈ 10¹² Ω m, sulfur ≈ 10¹⁵ Ω m.
Copper is used for wiring because of its low resistivity and reasonable cost.
Resistivity depends on temperature. All values above are at room temperature.

Examiner Tips and Tricks

You will not need to memorise specific resistivity values.
They will be given in the question.
But you should know the order of magnitudeThe powerThe rate of energy transfer. Measured in watts (W). of ten closest to the value of a quantity. Used for rough comparisons and estimation.: metals ~10⁻⁸, semiconductorsMaterials with resistivity between conductors and insulators. Their number densityMass per unit volume of a material. Measured in kg m⁻³. of charge carriers increases with temperature. ~10⁰ to 10³, insulators ~10¹² to 10¹⁵.