Simple drift speed probem driving me nuts

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SUMMARY

The discussion revolves around calculating the drift speed of electrons in a silver wire with a current of 200 mA and a radius of 0.8 mm. The correct drift speed, as stated in the reference material, is 1.07 x 10^-5 m/s, while the user initially calculated 1.06 x 10^-4 m/s due to an incorrect value for the density of silver. The user applied the equations J = I/A and J = nev_d to derive the drift speed but miscalculated the number density of particles. The correct approach involves using the accurate density of silver for precise calculations.

PREREQUISITES
  • Understanding of electric current and drift speed concepts
  • Familiarity with the formula J = I/A
  • Knowledge of the number density calculation using n = p*Avg/M
  • Basic understanding of the properties of silver, including its density
NEXT STEPS
  • Review the calculation of drift speed using J = nev_d
  • Learn about the properties of silver, including its density and atomic mass
  • Explore the relationship between current, area, and drift speed in conductive materials
  • Practice similar problems involving drift speed and number density calculations
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone involved in electrical engineering or materials science, particularly those studying electron behavior in conductive materials.

ttran1117
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Homework Statement


A current of 200 mA flows in a silver wire of radius 0.8mm. Find (a) the drift speed of the electrons. (b) the number density of particles.

Homework Equations


The Attempt at a Solution


The answer in the book is 1.07 x 10^-5, but I'm getting 1.06 x 10^-4. Can anyone tell me what I'm doing wrong?

So, I have J = I/A and J=nev_d ==> v_d = J/(ne)
J = 200 x 10^-3/pi(0.8x10^-3)^2

n = p*Avg/M
= 1.05 * 6.022 x 10^23 / 107.868 x 10^-3

plugging in for v_d, I get 1.06 x 10^-4.

This problem is supposed to be simple, but it's driving me nuts! Someone help please! Thanks a lot
 
Physics news on Phys.org
You used wrong value for the density of silver.

ehild
 

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