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direction of current density and normal vector

Posted 3 avr. 2013, 07:38 UTC−4 Version 4.3a 2 Replies

Andrea Marie Scholl
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Dear all,

I have a question as regards the direction of the current density:

I want to calculate the current density of an electrode which has the form of a cube.
Obviously I have 6 planes with a normal vector in + resp. - x, y and z direction.

Please imagine the following case:
I want to calculate the current density of the plane with a normal vector showing in -x direction. Do I have to multiply the result of my current density with -1 as I'm intrested in the -x direction and not the +x direction?

I'm a bit confused as regards the direction of the Jx, Jy and Jz current densities.
Can anyone please help me?


Thank you!
2 Replies Last Post 16 oct. 2013, 00:38 UTC−4
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 3 avr. 2013, 09:22 UTC−4

Hi Andrea,

the normal current density is a scalar resulting from the dot product n.j , n being the normal vector of the electrode surface and j being the current density vector. So the sign is defined with regard to the normal vector. A normal current density directed out of the electrode must be positive, regardless of it's direction in the models cartesian coordinate system, given the normal vector points to the outside.

Cheers
Edgar

--
Edgar J. Kaiser
www.emphys.com
Hi Andrea, the normal current density is a scalar resulting from the dot product n.j , n being the normal vector of the electrode surface and j being the current density vector. So the sign is defined with regard to the normal vector. A normal current density directed out of the electrode must be positive, regardless of it's direction in the models cartesian coordinate system, given the normal vector points to the outside. Cheers Edgar -- Edgar J. Kaiser http://www.emphys.com
Natasa Arefi
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Posted: 1 decade ago 16 oct. 2013, 00:38 UTC−4
Hello,

I have the same problem as Andrea. To investigate the amount of current delivered through an electrode I simulated a simple model.

The model consists of three cubes with unit dimension connected to each other. The center cube has these electrical properties:

Conductivity: 233260e-6
Relative permittivity: 17.719000e6

And the other two cubes have the following properties:

Conductivity: 1.45e6
Relative permittivity: 1

Imagine a semi-conductor material between two electrodes. Terminal was set to be equal to I_0=wv1(t[1/s]) in which wv1 is a square waveform with angular frequency equal to 314.15 rad/sec and amplitude equal to 5.
As you can see in the attached figure, there are negative current densities for the surface shown in the figure. How can we interpret such a negative current densities? How can we calculate current flowing through electrode having current density?

Kind regards,


Hello, I have the same problem as Andrea. To investigate the amount of current delivered through an electrode I simulated a simple model. The model consists of three cubes with unit dimension connected to each other. The center cube has these electrical properties: Conductivity: 233260e-6 Relative permittivity: 17.719000e6 And the other two cubes have the following properties: Conductivity: 1.45e6 Relative permittivity: 1 Imagine a semi-conductor material between two electrodes. Terminal was set to be equal to I_0=wv1(t[1/s]) in which wv1 is a square waveform with angular frequency equal to 314.15 rad/sec and amplitude equal to 5. As you can see in the attached figure, there are negative current densities for the surface shown in the figure. How can we interpret such a negative current densities? How can we calculate current flowing through electrode having current density? Kind regards,

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