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What is the resistivity of a material?
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Resistivity is a measure of how strongly a material opposes the flow of electric current. It is represented by the symbol ‘ρ’ (rho) and is measured in ohm-meters (Ω⋅m).
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How does temperature affect the resistivity of conductors?
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As temperature increases, the resistivity of conductors generally increases. This is because the increased thermal energy causes more collisions among atoms, scattering the electrons and impeding the flow of electric current.
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What is the difference between resistivity and resistance?
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Resistivity is a material property determining how much it resists current flow. Resistance, on the other hand, is the actual opposition encountered in a specific piece of material, calculated using resistivity, length, and cross-sectional area.
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Discuss the effect of temperature on the resistivity of semiconductors.
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In semiconductors, resistivity decreases with an increase in temperature. This occurs because higher temperatures provide more energy to electrons, facilitating their movement across the material lattice.
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How is resistivity measured in materials?
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Resistivity is measured using a formula that considers the resistance, length, and cross-sectional area of the material: ρ = R(A/L). Accurate measurement often involves using a four-point probe method to eliminate contact resistance.
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What units are used for resistivity?
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The unit for resistivity is ohm-meter (Ω⋅m). It can also be expressed in ohm-centimeter (Ω⋅cm) for smaller scales, but the standard international system uses Ω⋅m.
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Can you name a material with high resistivity?
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Rubber is an example of a material with high resistivity, making it a good insulator. Its high resistivity impedes the flow of electric current, preventing easy passage of electricity.
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Describe a material with low resistivity and its application.
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Copper has low resistivity, making it an excellent conductor widely used in electrical wiring. Its low resistivity means minimal resistance to electrical flow, maximizing efficiency in circuits.
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What factors influence the resistivity of a material?
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The resistivity of a material is influenced by temperature, material composition, and impurities present within the material. Each of these factors affects how easily charges can move through the material.
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What does a negative temperature coefficient of resistivity indicate?
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A negative temperature coefficient of resistivity indicates that a material's resistivity decreases with an increase in temperature, typical for semiconductors and some insulators.
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How is resistivity related to conductivity?
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Resistivity is inversely related to conductivity. High resistivity corresponds to low conductivity and vice versa. The equation linking them is: σ = 1/ρ, where σ is conductivity and ρ is resistivity.
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What is the resistivity of silicon at room temperature?
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The resistivity of silicon at room temperature is approximately 640 Ω⋅m, although this can vary based on the purity and doping of the silicon material.
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How does impurity concentration affect a material's resistivity?
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Increased impurity concentration in a material can significantly alter its resistivity, either increasing it in metals or decreasing it in semiconductors by adding free charge carriers.
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What role does resistivity play in material selection for electrical applications?
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Resistivity helps determine whether a material should be used as a conductor or insulator in electrical applications. Low resistivity materials suit conductors, while those with high resistivity are used as insulators.
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Explain the relationship between resistivity and cross-sectional area.
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Resistivity itself is independent of the cross-sectional area, but resistance depends on it. Increasing the cross-sectional area reduces resistance, but the material’s resistivity remains unchanged.
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