Final answer:
Electric resistivity is a measure of how strongly a material opposes electric current flow, while conductivity is its ability to conduct current. These properties are key in material selection for electronic components, as they determine whether a material is a good conductor, semiconductor, or insulator.
Step-by-step explanation:
Electric resistivity is a property of materials that quantifies how strongly they oppose the flow of electric current. It is denoted by the symbol ρ (rho) and has units of ohm-meters (Ω·m). When a voltage is applied, an electrical field arises, and the current density that results depends on this field and the material's properties. For good conductors like copper, silver, and gold, electric resistivity is low, meaning they allow electric charge to move easily through them, while good insulators have high resistivity, impeding charge flow. Conductivity is the inverse of resistivity and measures a material's ability to conduct electric current. It is of importance in selecting materials because the electrical performance of a device or system depends heavily on the appropriate selection of conductive, semiconductive, or insulative materials.
Semiconductors, like silicon and germanium, have intermediate resistivity values; their ability to conduct electricity can be altered significantly by introducing impurities, a property exploited in modern electronics. For example, adding impurities to silicon can decrease its resistivity, which is essential for creating components like diodes and transistors. Therefore, understanding a material's resistivity and conductivity is critical in engineering and technology, particularly in designing and manufacturing electronic devices.