Why tem mode not exist in rectangular waveguide

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te, tm tem modes ppt
tem mode in rectangular waveguide

Since such a current source is absent and waveguide being a single conductor configuration, TEM mode cannot exist inside a waveguide. Also it is evident A TEM mode has the electric field and the magnetic field normal to the direction of propagation. There is no component of either in the direction of Waveguides are hollow pipes, and may have either circular or rectangular The TEM mode cannot propagate in these single conductor transmission lines.