Calculating current given the current density and area

Click For Summary
SUMMARY

The discussion revolves around calculating the current in a wire given a current density of 6.67 × 10^6 A/m² and a cross-sectional area of 1.41 mm². The correct formula for current is applied: Current = current density * area, resulting in a calculated current of 9404.7 A. The second part of the problem involves determining the time required for 4.77 × 10²⁰ electrons to pass a point in the wire, using the formula time = charge / current, which yields a time of 0.00813 seconds. The error identified was a misunderstanding of unit conversion, specifically that 1 mm² equals 10^-6 m².

PREREQUISITES
  • Understanding of current density and its units
  • Familiarity with the formula for calculating current
  • Knowledge of charge and its relation to current and time
  • Ability to convert between units of area (mm² to m²)
NEXT STEPS
  • Review the principles of current density and its applications in electrical engineering
  • Practice unit conversions, specifically from mm² to m²
  • Explore the relationship between charge, current, and time in electrical circuits
  • Investigate common errors in calculations involving physical quantities and units
USEFUL FOR

Students studying physics, electrical engineering students, and anyone interested in understanding current flow in conductive materials.

CivilSigma
Messages
227
Reaction score
58
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: Current = 6.67\cdot10^6 A/m^2 * 1.41\cdot10^{-3} =9404.7A
For the second part I get: time=\frac{4.77*10^{20} electrons \cdot 1.602\cdot10^{-19} C/electron}{9404.7A}=0.00813s

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
 
Physics news on Phys.org
sakonpure6 said:
Do you see a math error?
Yes. Check your units one more time.
 
  • Like
Likes   Reactions: berkeman
Thank you, know I know 1mm^2=10^-6 m^2
 

Similar threads

  • · Replies 16 ·
Replies
16
Views
1K
  • · Replies 0 ·
Replies
0
Views
1K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
6
Views
2K
  • · Replies 23 ·
Replies
23
Views
6K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K