- #1
yungman
- 5,718
- 240
I want to verify the mechanism to which a varying E can induce voltage into a shielded coax.
According to Maxwell
[tex] \nabla \times \vec E = -\frac{\partial \vec B}{\partial t} \;\hbox { and }\; \nabla \cdot \vec E = \frac{\rho_{free}}{\epsilon}[/tex]
From this, with varying E, you induce varying charge density onto the outer shield which create a varying current onto the shield. But the inner conductor is partially shielded by the shield don't see as much E so the current induced is not as much. Therefore there is a difference in the two currents which create the voltage into the coax.
At the same time, with a 200V/m varying E there MUST be B associated with the E by the Maxwell
[tex] \nabla \times \vec B = \mu\vec J +\frac{\partial \vec E}{\partial t} [/tex]
But B induce equal current in both the inner conductor and the outer shield. This is common mode and don't matter.
Is this the mechanism?
According to Maxwell
[tex] \nabla \times \vec E = -\frac{\partial \vec B}{\partial t} \;\hbox { and }\; \nabla \cdot \vec E = \frac{\rho_{free}}{\epsilon}[/tex]
From this, with varying E, you induce varying charge density onto the outer shield which create a varying current onto the shield. But the inner conductor is partially shielded by the shield don't see as much E so the current induced is not as much. Therefore there is a difference in the two currents which create the voltage into the coax.
At the same time, with a 200V/m varying E there MUST be B associated with the E by the Maxwell
[tex] \nabla \times \vec B = \mu\vec J +\frac{\partial \vec E}{\partial t} [/tex]
But B induce equal current in both the inner conductor and the outer shield. This is common mode and don't matter.
Is this the mechanism?