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How to plot fields inside round wire REVIEWED
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Short working note by Phil dated 12.12.13, tied to Appendix D of his transmission lines notes. It sketches how to build the real transverse E field at z = 0 from the complex Er and Eφ components, using the rotation from polar to Cartesian unit vectors. It observes that at a fixed point the vector traces an ellipse, suggests plotting a sequence of 2D arrow graphs, and ends with an inconclusive complex-form attempt.
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How to plot the transverse electric field in a round wire PhL 12.12.13
This never got much off the ground. I proposed the reader do it at the end of Appendix D.
I have not done this, but I think this is how you could do it. First, pick z = 0. Then I think we have
Etransverse(r,φ) = cos(-ωt+mφ + arg[Eφ(r)] ) |Eφ| + cos(-ωt +mφ + arg[Er(r)] ) |Er|
Then use
e'1 = cosφ e1 + sinφ e2
e'2 = - sinφ e1 + cosφ e2
Proof #1:
to replace
= -sinφ + cosφ
= cosφ + sinφ
and then you have
Etransverse(r,φ) = cos(-ωt + mφ + arg[Eφ(r)] ) |Eφ| [-sinφ + cosφ ]
+ cos(-ωt + mφ + arg[Er(r)] ) |Er| [cosφ + sinφ ]
and then given the complex expressions for Er(r,m) and Eφ(r,m), you could plot the actual physical transverse electric field vector Etransverse(r,φ) at this instant in time. This is for z = 0. The vector's direction and magnitude will change with t in a complicated way.
Ah, but for fixed r and φ this has the form
Etransverse(r,φ) = cos(ωt - a) + cos(ωt - b)
and I now know this describes an ellipse. So at any point, the Et vector goes in an ellipse. This suggests to me that if you had a Maple arrow graph animation, the arrows would move in a very complicated way. The "current" in the wire then looks different geometrically at each instant in time! So you would have to print out a sequence of 2D arrow graphs to get the nature of things.
Idea. Go back to the complex form
Et = ejmφe-jωt(Eφ + Er )
= ejmφ e-jωt(Eφ[-sinφ + cosφ ] + Er [cosφ + sinφ ] )
= ejmφ e-jωt( (Ercosφ - Eφsinφ) + (Er sinφ + Eφcosφ) )
Well never mind, there is no Er±jEφ sitting here.