Current Density in a Wire

  • Thread starter 123yt
  • Start date
  • #1
32
0

Homework Statement


A long straight wire with circular cross-section and a diameter of 5.10 mm is made of a metal with resistivity = 5.00×10-8 m. The wire carries a current of 28.5 A. Calculate the current density in the wire.


Homework Equations


J = i / A


The Attempt at a Solution


I took the surface area, 0.0051 m, and multiplied it by pi to get the circumference. Then, I divided the current by the circumference and got 1778.79 A/m^2.

It's incorrect.
 

Answers and Replies

  • #2
berkeman
Mentor
59,496
9,625

Homework Statement


A long straight wire with circular cross-section and a diameter of 5.10 mm is made of a metal with resistivity = 5.00×10-8 m. The wire carries a current of 28.5 A. Calculate the current density in the wire.


Homework Equations


J = i / A


The Attempt at a Solution


I took the surface area, 0.0051 m, and multiplied it by pi to get the circumference. Then, I divided the current by the circumference and got 1778.79 A/m^2.

It's incorrect.

5.1mm is the diameter, not the area, so multiplying it by PI does indeed give you the circumference. But circumference is not the area.

Please try again, and get your terms for diameter, area, and current density (current divided by the cross-sectional area) correct....
 
  • #3
berkeman
Mentor
59,496
9,625
Also, the units for resistivity are not meters....
 
  • #4
32
0
Yeah, sorry, copy and pasted the question weirdly.

Anyways, thanks for the correction. I got it figured out now.
 

Related Threads on Current Density in a Wire

  • Last Post
Replies
3
Views
6K
  • Last Post
Replies
5
Views
3K
Replies
1
Views
8K
Replies
5
Views
14K
Replies
1
Views
1K
  • Last Post
Replies
12
Views
3K
  • Last Post
Replies
6
Views
20K
Top