Electrical Resistivity and Conductivity Quiz
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Questions and Answers

What term represents the resistivity of a metal at 0°C?

  • ρT
  • ρr
  • ρ0C (correct)
  • αT
  • How does an increase in temperature affect the resistivity of a metal?

  • Causes a phase change
  • Decreases it
  • Increases it (correct)
  • Has no effect
  • What does the residual component of electrical resistivity in a metal result from?

  • Presence of impurity atoms (correct)
  • Alignment of grains
  • Doping with other materials
  • Increase in temperature
  • How does close proximity of atoms influence electron energy bands in a solid material?

    <p>Splits each atomic state into electron energy bands</p> Signup and view all the answers

    Which factor becomes significant only at low temperatures in determining the total resistivity of a metal?

    <p>Residual component</p> Signup and view all the answers

    What happens to the vibration amplitude of positive-ion cores as the temperature of a metal increases?

    <p>Increases</p> Signup and view all the answers

    What mainly determines the conductivity of a material?

    <p>Energy band structure</p> Signup and view all the answers

    In a semiconductor, where does an electron transition to when enough energy is supplied?

    <p>Conduction band</p> Signup and view all the answers

    What type of material has conductivities between good conductors and insulators?

    <p>Semiconductors</p> Signup and view all the answers

    How does the resistivity of a semiconductor change with increasing temperature?

    <p>Decreases</p> Signup and view all the answers

    What can valence electrons in a semiconductor become under certain conditions?

    <p>Free electrons</p> Signup and view all the answers

    What determines the specific properties of a semiconductor?

    <p>Impurities added to it</p> Signup and view all the answers

    What is the material constant that relates quantities such as resistance, length, and cross-sectional area in a conductor?

    <p>Electrical resistivity</p> Signup and view all the answers

    At room temperature, which type of material exhibits the highest electrical conductivity?

    <p>Pure metals</p> Signup and view all the answers

    What range of values characterizes the conductivity of insulators at room temperature?

    <p>10-10 to 10^-20 (Ω.m)^-1</p> Signup and view all the answers

    What is the relationship between resistivity and temperature in materials?

    <p>Resistivity increases with temperature.</p> Signup and view all the answers

    What is the electrical conductivity range of semiconductors at room temperature?

    <p>10-6 to 10^4 (Ω.m)^-1</p> Signup and view all the answers

    What component of resistivity accounts for the increase in resistivity when temperature rises?

    <p>Thermal resistivity component</p> Signup and view all the answers

    Study Notes

    Electrical Resistivity

    • Electrical resistivity (ρ) is a material constant that depends on temperature.
    • The units for electrical resistivity are ohm-meters (Ω.m).
    • ρT = ρ0C(1+ αTT) where ρ0C is resistivity at 0°C, αT is the coefficient of resistivity, and T is the temperature of the metal.

    Factors Affecting Resistivity

    • As the temperature of a metal increases, the vibration of the positive-ion cores increases, causing the release of photons that scatter conduction electrons and increase resistivity.
    • Resistivity also increases due to structural imperfections like dislocations, grain boundaries, and impurity atoms.

    Energy Band Structure in Solids

    • When atoms come close together, electrons are perturbed by adjacent atoms, resulting in a series of closely spaced electron states termed an electron energy band.
    • Each atomic state splits into a band consisting of multiple states.

    Conductivity

    • Conductivity depends on two factors: atomic bond and energy band structure.
    • Metals have high conductivity due to strong ionic bonds and a small energy gap between the valence and conduction bands.
    • Semiconductors have low conductivity due to weaker covalent bonds and a larger energy gap.
    • Insulators have very low conductivity due to strong covalent bonds and a large energy gap.

    Semiconductors

    • Semiconductors are materials with conductivity between good conductors and insulators.
    • The resistivity of a semiconductor decreases as temperature increases.
    • Semiconductor properties depend on the impurities or dopants added to the material.
    • At higher temperatures, semiconductors act like conductors, and at lower temperatures, they act like insulators.

    Ohm's Law

    • Electrical conductivity (σ) is a measure of the ability of a material to conduct electricity.
    • The units for electrical conductivity are (ohm-meter)^-1 or (Ω.m)^-1.
    • Ohm's Law relates electrical conductivity, resistivity, and the passage of electric current.

    Electrical Conductivity of Materials

    • Pure metals like silver, copper, and gold have the highest conductivities (about 10^7 (Ω.m)^-1).
    • Electrical insulators like polyethylene and polystyrene have very low conductivities (about 10^-14 (Ω.m)^-1).
    • Semiconductors like silicon and germanium have conductivities in between (about 10^-6 to 10^4 (Ω.m)^-1).

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    Description

    Test your knowledge on electrical resistivity, which is a material constant related to resistance based on the length and cross-sectional area of a conductor. Explore the concept of electrical conductivity as an alternative to resistance in understanding electric current flow.

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