Relationship between current, drift velocity and thermal velocity

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Discussion Overview

The discussion focuses on the relationship between current, drift velocity, and thermal velocity in a solid cylindrical resistor, specifically using copper at room temperature as an example. It explores theoretical aspects and mathematical relationships among these quantities.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants note that drift velocity and current are proportional, while the thermal speed is dependent on temperature and does not significantly affect current.
  • One participant requests a formula to clarify the relationships among these quantities.
  • Another participant provides a formula for thermal velocity as sqrt(3kT/m) and discusses the relationship between current and drift velocity using the equation I = vnqA, where n is electron concentration, q is charge, and A is cross-sectional area.
  • The participant also explains the relationship in terms of current density, J = vnq, relating particle flux to concentration and velocity.

Areas of Agreement / Disagreement

Participants generally agree on the proportional relationship between drift velocity and current, but there is no consensus on the implications of thermal velocity or its effect on current.

Contextual Notes

The discussion does not clarify the assumptions underlying the relationships or the specific conditions under which these formulas apply, nor does it address potential limitations in the models presented.

yanyin
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for a normal solid cylindrical resistor, made of say copper, at room temperature, describe the relationshop between the current in the conductor, the drift velocity of conduction electrons in the conductor, and the thermal velocity of conduction electrons in the conductor.
 
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The drift velocity and current are proportional. The thermal speed depends on the temperature. Current is not much affected.
 
could u give a formula pls
 
The thermal energy is 3/2 kT, so equating that to kinetic energy, thermal velocity is sqrt(3kT/m), on the order of 10^5 m/s at room temperature.

The drift velocity is related to current like I = vnqA, where n is the concentration (per volume), of electrons, q is the charge. In terms of current density, J = vnq. Current density is charge per second per area, so dividing both sides by q relates a particle flux on the left hand side to a concentration times a velocity on the right. This is a general relationship in kinetics.
 

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