The resistance of pure metals ___________

Question

Examoogle · Accepted Answer

Increases with an increase in temperature

Explanation: Pure metals exhibit a positive temperature coefficient of resistance, meaning their electrical resistance increases as the ambient temperature rises. This behavior occurs because the resistivity of a metal is directly dependent on the scattering of electrons due to thermal vibrations of the lattice.

Working Principle: In a metallic crystal lattice, increasing the temperature enhances the vibrational kinetic energy of the atoms (phonons). These vibrations increase the probability of collisions between free conduction electrons and the lattice ions, effectively decreasing the mean free path of the electrons and increasing the material's resistance.

Key Formulas: $R_t = R_0(1 + \alpha \Delta T)$ — Relationship between resistance and temperature; $\alpha = \frac{R_t - R_0}{R_0 \Delta T}$ — Definition of temperature coefficient of resistance

Key Points: Pure metals have a positive temperature coefficient (PTC).; Insulators and semiconductors typically exhibit a negative temperature coefficient (NTC).; Resistance change is approximately linear for a moderate temperature range.

Advantages: Used in RTDs (Resistance Temperature Detectors) for precise temperature measurement; Allows for stable electrical heating elements

Disadvantages: Efficiency loss in power lines due to increased resistance at high temperatures; Thermal runaway potential in certain circuit applications

Applications: Resistance Temperature Detectors (RTD); Electrical heating elements; Fuses and circuit protection

Additional Info: Most pure metals like Copper, Aluminum, and Gold follow this trend.. Option B describes semiconductors and insulators (NTC materials), not pure metals.

Answer: A is correct — The resistance of pure metals increases with temperature due to increased electron-lattice scattering.

Exam Tip: Always remember that pure metals behave as PTC materials, while semiconductors (like Germanium or Silicon) are NTC. This distinction is a favorite topic in both electrical and solid-state physics exams.

Related Questions

Discussion (0)