Calculating current given the current density and area

A/m^2 * 1.41*10^-6 m^2 = 9404.7A, and for the second part, time=4.77*10^20 electrons * 1.602*10^-19 C/electron / 9404.7A = 5.08sIn summary, the conversation is about a problem involving a wire with a current density of 6.67 × 10^6 A/m^2 and a cross-sectional area of 1.41 mm^2. The question is asking for the current that the wire carries and how much time is required for a specific number of electrons to pass through any point on the wire
  • #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
 
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  • #2
sakonpure6 said:
Do you see a math error?
Yes. Check your units one more time.
 
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  • #3
Thank you, know I know 1mm^2=10^-6 m^2
 

1. What is current density?

Current density is a measure of the amount of electric current flowing through a given area. It is represented by the symbol J and is typically measured in amps per square meter (A/m^2).

2. How is current density calculated?

To calculate current density, you divide the current (I) by the cross-sectional area (A) of the conductor. The formula is J = I/A. This will give you the current density in amperes per square meter (A/m^2).

3. Can current density vary within a conductor?

Yes, current density can vary within a conductor. It is dependent on the cross-sectional area of the conductor. In a uniform conductor, the current density will be constant. But in a non-uniform conductor, the current density will vary at different points along the conductor.

4. What is the relationship between current, current density, and cross-sectional area?

The relationship between current, current density, and cross-sectional area is directly proportional. This means that as the current or cross-sectional area increases, the current density will also increase. Similarly, if the current or cross-sectional area decreases, the current density will decrease.

5. How is current density used in practical applications?

Current density is an important concept in electrical engineering and is used to design and optimize electrical systems. It is also used in materials science to understand the behavior of conductors. In practical applications, current density is used to determine the appropriate size of conductors to carry a given amount of current without overheating.

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