Current Density and Electron Drift Speed

In summary, a 1.5 mm X 1.5 mm square aluminum wire has a current of 1.10 A. The current density can be calculated using J = I/A, giving a value of 488,889 mA/m^2. The electron drift speed can be found using Vd = J/ne. However, the question specifies the answer should be in MA/m^2, so the current must be converted to mA before being divided by the area. The correct answer is 0.489 MA/m^2. The confusion could have been avoided if the units were specified clearly in the question.
  • #1
amb0027
11
0

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?
 
Physics news on Phys.org
  • #2
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.
 
  • #3
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.
 
  • #4
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?
 
  • #5
0.489 MA/m2
 
  • #6
so M is 10^6? ooh yea.. thanks!
 
  • #7
Ironic how a small thing like M vs. m can cause such a difficulty.
 
  • #8
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
 

FAQ: Current Density and Electron Drift Speed

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 calculated by dividing the current (I) by the cross-sectional area (A) through which it is flowing: J = I/A. It is typically measured in amperes per square meter (A/m^2).

2. How is current density related to electron drift speed?

Current density is directly related to electron drift speed. As electric current flows through a material, it is carried by the movement of electrons. The higher the current density, the faster the electrons are moving. This is because a higher current density means that more electrons are flowing through a given area, increasing the overall speed of electron drift.

3. What factors affect current density?

The two main factors that affect current density are the material through which the current is flowing and the amount of current itself. Different materials have different conductivities, which can impact the flow of electrons and thus the current density. Additionally, increasing the amount of current will also increase the current density.

4. How is current density measured?

Current density can be measured using a variety of methods, depending on the specific application. One common method is to use a current probe, which is a device that can be attached to a circuit to measure the current passing through it. Another method is to use a Hall effect sensor, which measures the magnetic field produced by the flowing current and can then calculate the current density.

5. What is electron drift speed?

Electron drift speed is the average speed at which electrons move through a material in response to an electric field. It is typically much slower than the speed of individual electrons, as they constantly collide with atoms and other particles in the material. The exact speed varies depending on the material and the strength of the electric field, but it is typically on the order of millimeters per second.

Similar threads

Find the drift speed of of the electrons
Replies
7
Views
1K
Find Electron Current Through Iron Wire
Replies
1
Views
10K
Exploring the Drift Speed of Electrons in Conductors
Replies
6
Views
2K
Finding the electron drift speed
Replies
2
Views
2K
Find the magnitude of the current density
Replies
11
Views
4K
Finding the drift speed of a conduction electrons
Replies
13
Views
2K
Electron drift speed, Current, and Electric field in hollow wire?
Replies
1
Views
10K
How can an increase in area cause a decrease in drift speed?
Replies
6
Views
4K
Electron Drift Velocity in Semiconductors
Replies
1
Views
2K
Calculating Electric Field from Electron Drift and Diffusion in Si Sample"
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top