Surface Charge in MHD

sina_mech · March 27, 2015, 16:59

Hi,

In MHD module, you have to put Volume charge density (C/m3) for particles. So what if we want to use surface charge density (C/m2) ?

PS : The force on the particle in a electric field is : F = qE, in which q is particle charge.

`e` · March 30, 2015, 03:06

Why not simply convert your surface charge density to a volume charge density value?

sina_mech · March 30, 2015, 03:10

For example for a spherical particle of diameter 2e-5 m, and surface charge of 7e-4 C/m2 , the volume charge density will be something around 200 C/m3. and I just feel that 200 C/m3 seems to be really high!

`e` · March 30, 2015, 03:30

Yes, from some algebra we can find that for a spherical particle a relationship exists between the volume charge density,

, surface charge density,

, and radius of the particle,

:

$q_v = {3 \over r} q_s$

I'm not familiar with typical orders of magnitude for surface/volume charge densities but math doesn't lie!

March 27, 2015, 16:59	Surface Charge in MHD	#1
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 16	Hi, In MHD module, you have to put Volume charge density (C/m3) for particles. So what if we want to use surface charge density (C/m2) ? PS : The force on the particle in a electric field is : F = qE, in which q is particle charge.

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March 30, 2015, 03:06		#2
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	Why not simply convert your surface charge density to a volume charge density value?

March 30, 2015, 03:10		#3
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 16	For example for a spherical particle of diameter 2e-5 m, and surface charge of 7e-4 C/m2 , the volume charge density will be something around 200 C/m3. and I just feel that 200 C/m3 seems to be really high!

March 30, 2015, 03:30		#4
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	Yes, from some algebra we can find that for a spherical particle a relationship exists between the volume charge density, , surface charge density, , and radius of the particle, : $q_v = {3 \over r} q_s$ I'm not familiar with typical orders of magnitude for surface/volume charge densities but math doesn't lie!