about AC signal calculations in Comsol

Hi all,

I am curious about AC signals in Comsol.

Why do we need to add an analytic function from the functions subtitle to work with an AC signal?
I added a waveform of square wave. If I do not place it in analytic function, the program couldn't calculate the jakobian, thus doesn't work.

Simply, why adding a waveform only does not work?

thanks a lot.


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physics undergrad
loves photon.