A transmission-lin system involving two lines?

[muaythai2006]

Vg is a constant voltage source of 100 V. Find and sketch: a) the line voltage versus z for t=.2 mircro. second.

I know how to do it if there is no left portion(Z=-300 m to Z=0 m)...I did some problems involving one line...but this one is two lines...Can u guy help me out....

 

[jallem]

The right arm has total propagation time of 300 m/3e8 m/s = 1 µsec
and for the left arm the propagation time is 300m/2*10^8 m/s = 1.5 µsec
For t=0.2 µsec the pulse had traveled toward the right 60 m and
toward the left by 40 m. The pulse amplitude is 100(2/5)V=40V