What is the magnitude of the current density across A1 ?

AI Thread Summary
The discussion focuses on calculating the current density across a circular conductor with a current of 5.00 A and a radius of 0.400 cm at cross-section A1. The formula used is J = I/A, resulting in a current density of approximately 99,472.8 A/m². A participant points out that the calculation is correct, but the units should be expressed as A/m² instead of A m². Additionally, the problem poses a question about the radius at A2, where the current density is one-fourth that of A1. The conversation emphasizes the importance of correct unit representation in calculations.
zooropa
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Homework Statement



The figure represents a section of a circular conductor of nonuniform diameter carrying a current of 5.00 A. The radius of cross-section A1 is 0.400 cm.
[URL=http://img97.imageshack.us/i/img01mn.jpg/][PLAIN]http://img97.imageshack.us/img97/7220/img01mn.th.jpg[/URL][/PLAIN]


Homework Equations



(a) What is the magnitude of the current density across A1 ?
(b) If the current density across A2 is one-fourth the value across A1, what is the radius of the conductor
at A2 ?

The Attempt at a Solution



J=I/A= 5.00A/pi(.004)^2=99,472.8 A m^2
Could someone help please? I am doing this the right way?
 
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zooropa said:

Homework Statement



The figure represents a section of a circular conductor of nonuniform diameter carrying a current of 5.00 A. The radius of cross-section A1 is 0.400 cm.
[URL=http://img97.imageshack.us/i/img01mn.jpg/][PLAIN]http://img97.imageshack.us/img97/7220/img01mn.th.jpg[/URL][/PLAIN]


Homework Equations



(a) What is the magnitude of the current density across A1 ?
(b) If the current density across A2 is one-fourth the value across A1, what is the radius of the conductor
at A2 ?

The Attempt at a Solution



J=I/A= 5.00A/pi(.004)^2=99,472.8 A m^2
Could someone help please? I am doing this the right way?

Looks correct so far, except for the units of your answer -- should be A/m^2. You did the right thing in the division, just left out the "/" in the final answer's units.
 
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