The reciprocal of resistivity is________

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Conductivity

Explanation: The reciprocal of resistivity ($\rho$) is defined as conductivity ($\sigma$). It measures a material's ability to conduct an electric current, representing the ease with which charge carriers flow through a substance.

Working Principle: In a conductor, resistivity represents the opposition to current flow per unit length and area. Conductivity is the inverse characteristic; as a material's atomic structure allows for higher mobility of free electrons, its resistivity decreases, thereby increasing its conductivity.

Key Formulas: $\sigma = \frac{1}{\rho}$ — Relationship between conductivity ($\sigma$) and resistivity ($\rho$); $R = \rho \frac{l}{A}$ — Resistance formula involving resistivity

Key Points: The SI unit of conductivity is Siemens per meter (S/m).; Metals like copper and silver have high conductivity and low resistivity.; Conductivity is a temperature-dependent property in metals, usually decreasing as temperature increases.

Advantages: Quantifies the efficiency of current flow in materials.; Used extensively in selecting materials for transmission lines and electronics.

Disadvantages: High conductivity does not always imply high thermal conductivity.; Measurement is sensitive to temperature and material purity.

Applications: Semiconductor manufacturing (doping levels); Power transmission efficiency calculations; Electrolytic solution analysis

Additional Info: Option B is incorrect because Resistance (R) is the reciprocal of Conductance (G).. Option D is incorrect because Impedance (Z) is the total opposition to AC current, including resistance and reactance.

Answer: C is correct — Conductivity is defined as the mathematical reciprocal of resistivity.

Exam Tip: Always remember the inverse pairs: Resistivity-Conductivity ($\rho - \sigma$) and Resistance-Conductance ($R - G$). Resistivity is a material property, while Resistance is a component property.

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