The lumped circuit for a small section of the line can be any one of that shown below :
Note
For the analysis of the transmission to be valid at all frequencies,
should be much less than
at all frequencies. In other words
the analysis is to be carried out in the limit .
All above representations are equivalent in the limit .
has
= 
= 
= 
= 
should be much less than
at all frequencies. In other words
the analysis is to be carried out in the limit 
.
. 
