Calculating current given the current density and area

  • Thread starter CivilSigma
  • Start date
  • #1
CivilSigma
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Hello, I am having trouble getting the correct solution to the following problem, even though I think my steps all are correct! What did I do wrong?

1. Homework Statement

A wire has a current density of 6.67 × 10^6 A/m^2. If the cross-sectional area of the wire is 1.41 mm^2, what current does the wire carry?

With this current, how much time is required for 4.77 × 1020 electrons to pass any point on the wire?

Homework Equations


Current = current density * area
Current = charge/time So, time = charge / current

The Attempt at a Solution


For the first part I get: [tex]Current = 6.67\cdot10^6 A/m^2 * 1.41\cdot10^{-3} =9404.7A[/tex]
For the second part I get: [tex]time=\frac{4.77*10^{20} electrons \cdot 1.602\cdot10^{-19} C/electron}{9404.7A}=0.00813s[/tex]

And as I stated, I'm not getting the correct answer. As you can see my units all match up. Do you see a math error? Or have I misunderstood a concept.

Thank you,
-Sakon
 

Answers and Replies

  • #2
Bystander
Science Advisor
Homework Helper
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Do you see a math error?
Yes. Check your units one more time.
 
  • #3
CivilSigma
227
58
Thank you, know I know 1mm^2=10^-6 m^2
 

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