Current Density and Electron Drift Speed

AI Thread Summary
The discussion revolves around calculating the current density and electron drift speed for a square aluminum wire carrying 1.10 A of current. The current density is calculated using the formula J = I/A, where the area is 2.25 x 10^-6 m², resulting in a value of approximately 488,888.889 A/m². However, the confusion arises from the required unit of MA/m² instead of A/m², leading to the correct answer being 0.489 MA/m². Participants highlight the importance of unit conversions and the impact of minor details, such as the difference between 'M' and 'm', on problem-solving. Overall, the discussion emphasizes the significance of careful attention to units in physics calculations.
amb0027
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Homework Statement


The current in a 1.5 mm X 1.5 mm square aluminum wire is 1.10 A. What are (a) the current density and (b) the electron drift speed?


Homework Equations


current density: J = I/A
drift speed Vd = J/ne


The Attempt at a Solution


It's asking for an answer in MA/m^2.. when I divide I(1.1) by A(2.25 x 10^-6) I get 488,888.889. I tried the answer 489 and 488 and it says it's incorrect. Also tried 488,889 just to make sure.. still incorrect. Any help would be appreciated?
 
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amb0027 said:

Homework Statement


The current in a 1.5 mm X 1.5 mm square aluminum wire is 1.10 A. What are (a) the current density and (b) the electron drift speed?


Homework Equations


current density: J = I/A
drift speed Vd = J/ne


The Attempt at a Solution


It's asking for an answer in MA/m^2.. when I divide I(1.1) by A(2.25 x 10^-6) I get 488,888.889. I tried the answer 489 and 488 and it says it's incorrect. Also tried 488,889 just to make sure.. still incorrect. Any help would be appreciated?

Welcome to the PF.

When you say you "tried 488,889", you mean 488.889, right? Your answer looks correct to me.
 
If the answer should be in mA/m2, then use 1.10 A + 1.10×103 mA.

That would make your answer something like: 4.89×108 mA/m2.
 
Thanks for your replies. But it says MA/m^2, not mA/m^2. and the answer I've shared here does not work.. any other suggestions?
 
0.489 MA/m2
 
so M is 10^6? ooh yea.. thanks!
 
Ironic how a small thing like M vs. m can cause such a difficulty.
 
SammyS said:
Ironic how a small thing like M vs. m can cause such a difficulty.

Here are the difficulties of Physics

- Units
- Signs
- Wording of the question
- Conventions
 
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