Partial model of a resistance that links two generalized electrical connectors.
The model computes a resistance R(T) that varies depending on the temperature T as
R(T) = Rref (M + T)/(M + Tref),
where the resistance Rref is the reference value of the resistance,
M is the temperature coefficient of the cable material,
and Tref is the reference temperature.
The temperature T is the temperature of the heat port
if useHeatPort = true.