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Questions and Answers
According to the Drude model, what is the primary motion of electrons in a metal before the application of an electric field?
According to the Drude model, what is the primary motion of electrons in a metal before the application of an electric field?
What is the effect of collisions in a conductor based on the Drude model?
What is the effect of collisions in a conductor based on the Drude model?
What does the current density, J, quantify in a conductor?
What does the current density, J, quantify in a conductor?
What does the equation J = nqv (where v is drift velocity) assume about the charge carriers in a conductor?
What does the equation J = nqv (where v is drift velocity) assume about the charge carriers in a conductor?
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What is the relationship between current density (J) and electrical field (E) in a typical conductor?
What is the relationship between current density (J) and electrical field (E) in a typical conductor?
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What does the constant of proportionality σ (conductivity) represent in the equation J = σE?
What does the constant of proportionality σ (conductivity) represent in the equation J = σE?
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Which of the following is the correct unit of conductivity?
Which of the following is the correct unit of conductivity?
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What is used to represent the direction of the normal vector of a small tile on a surface?
What is used to represent the direction of the normal vector of a small tile on a surface?
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What does the flux of J = nqv through a surface represent?
What does the flux of J = nqv through a surface represent?
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How is the total flux through an arbitrary surface, S, calculated when the surface is divided into a number of tiny flat tiles?
How is the total flux through an arbitrary surface, S, calculated when the surface is divided into a number of tiny flat tiles?
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Study Notes
Section E5.2: A Model of Current Flow
- Electrons in metals are free to move within the conductor.
- The Drude model describes electron movement.
- Electrons have thermal velocities and random movement.
- An electric field causes a drift velocity that is opposite the field.
- Collisions create thermal energy.
- Mobile charged particles are called charge carriers.
Section E5.3: Current Density
- Current density (J) measures how quickly charge moves.
- J = ρvd = nqvd
- ρ is charge density (charge per unit volume) = nq
- n is number density of carriers
- q is charge of each carrier
- Vd is the drift velocity
- This equation assumes a single type of charge carrier.
- Multiple charge carriers: J = ρ1vd1 + ρ2vd2 +...
- Current density is proportional to the electric field: J = σE
- σ is conductivity
- Conductivity units are Ω-1m-1 or S/m
- Metal conductivity is typically high (6 x 107 Ω-1m-1).
- Plastic conductivity is typically lower.
Section E5.4: Flux
- Flux describes the rate at which something flows through a surface.
- Divide the surface into small, flat "tiles" (dĀ).
- Tile vector (dĀ) includes the area and the direction normal to the tile.
- Flux of a vector field (U) through a tile is U • dĀ
- Total flux through a surface S is the sum of flux through all tiles: ∫S U • dĀ
- If the particle density is n and velocity is v, flux of J through a surface is J • n = nqv.
- Flux of J = rate of charge flow through the surface.
- Flux of T = rate of energy flow through surface.
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Description
This quiz covers the Drude model of electron movement in conductors and the concept of current density. It explores key equations relating to charge carriers and their behavior under electric fields, as well as the relationship between current density and conductivity. Test your understanding of these fundamental concepts in physics.
