Podcast
Questions and Answers
What term represents the resistivity of a metal at 0°C?
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?
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?
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?
How does close proximity of atoms influence electron energy bands in a solid material?
Which factor becomes significant only at low temperatures in determining the total resistivity of a metal?
Which factor becomes significant only at low temperatures in determining the total resistivity of a metal?
What happens to the vibration amplitude of positive-ion cores as the temperature of a metal increases?
What happens to the vibration amplitude of positive-ion cores as the temperature of a metal increases?
What mainly determines the conductivity of a material?
What mainly determines the conductivity of a material?
In a semiconductor, where does an electron transition to when enough energy is supplied?
In a semiconductor, where does an electron transition to when enough energy is supplied?
What type of material has conductivities between good conductors and insulators?
What type of material has conductivities between good conductors and insulators?
How does the resistivity of a semiconductor change with increasing temperature?
How does the resistivity of a semiconductor change with increasing temperature?
What can valence electrons in a semiconductor become under certain conditions?
What can valence electrons in a semiconductor become under certain conditions?
What determines the specific properties of a semiconductor?
What determines the specific properties of a semiconductor?
What is the material constant that relates quantities such as resistance, length, and cross-sectional area in a conductor?
What is the material constant that relates quantities such as resistance, length, and cross-sectional area in a conductor?
At room temperature, which type of material exhibits the highest electrical conductivity?
At room temperature, which type of material exhibits the highest electrical conductivity?
What range of values characterizes the conductivity of insulators at room temperature?
What range of values characterizes the conductivity of insulators at room temperature?
What is the relationship between resistivity and temperature in materials?
What is the relationship between resistivity and temperature in materials?
What is the electrical conductivity range of semiconductors at room temperature?
What is the electrical conductivity range of semiconductors at room temperature?
What component of resistivity accounts for the increase in resistivity when temperature rises?
What component of resistivity accounts for the increase in resistivity when temperature rises?
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.
