Current Density: E,D,pv and Jz @ z=0 & z=.1m

In summary, the equations for E, D, and pv as functions of z are 120z^(1/3)az V/m, 1.062z^(1/3)az nC/m^2, and .354/z^(2/3) nC/m^3, respectively. The z component of the current density is 0 at z=0 and z=.1m. There may be discrepancies in the given solution for part b.
  • #1
oggrol
3
0
Let E=Eo (err...free space, not sure how to represent the symbols)
V=90z^(4/3) in the region z=0(Potential)
a) Find expressions for E,D and pv (volume charge density) as functions of z

My work:
E=-div V=0+0)120z^(1/3)az=120z^(1/3)az V/m
D=Eo E=1.062z^(1/3)az nC/m^2
pv=div D=.354/z^(2/3) nC/m^3

b)If the velocity of the charge density is given as vx=5x10^6 *z^(2/3) m/s, find Jz (current density) at z=0 and z=.1m

My work:
Now this is where I am confused because J=pv*v (volume charge density*velocity vector). And the book only gives the x component of the velocity vector and asks for the z component of the current density. If you ask me, that means the z component of the current density is 0, but I have no way of checking my answer.

:confused:

Is this correct?
 
Last edited:
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  • #2
Still not sure about part b of this one, and running into more problems with the stuff :cry:
 
  • #3
Teacher posted solutions today...

had Jz=Pv*Vx ...

Still don't believe that though unless it was a misprint in the book or something ... doesn't make sense to me
 

1. What is current density?

Current density is a measure of the amount of electric current flowing through a particular area. It is represented by the symbol J and is measured in amperes per square meter (A/m²).

2. How is current density calculated?

Current density can be calculated by dividing the total current (I) by the cross-sectional area (A) of the material through which the current is flowing. This is represented by the equation J = I/A.

3. What is the relationship between current density and electric field?

Current density and electric field are directly proportional to each other. This means that as the electric field increases, the current density also increases. This relationship is represented by the equation J = σE, where σ is the conductivity of the material.

4. How does current density vary with position in a material?

The current density can vary with position in a material depending on the electric field and the material's properties. In some materials, the current density may be constant, while in others it may vary significantly.

5. What is the significance of current density at z=0 and z=0.1m?

The values of current density at z=0 and z=0.1m represent the current flowing through the material at those specific points. This can be useful in understanding how the current is distributed within the material and how it may vary at different points.

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