Questions: Transmission lines

A cable of length metres with a polyethylene dielectric, ε_{r} has a characteristic impedance of ohms and a loss of ohms/metre, and is left open circuit at its far end. Given a constant drive voltage versus frequency, at what lowest frequency will the current into its near end be a maximum?

Review: Transmission line behaviour

A multi-core screened cable has a screen diameter of cm and a total inner wiring diameter of cm with a PVC insulation, ε_{r} . Ignoring losses, what is the cable's internal common mode transmission line characteristic impedance?

The same cable as in Q2 contains several wire pairs of 7/0.2mm (overall diameter including insulation of 1.2mm) with PVC insulation material, ε_{r} = 3. Ignoring losses, air gaps and coupling to other pairs, what is the differential mode transmission line impedance of each pair?

What will happen (to a first order) to the differential pair Z_{0} if the wire pairs of Q3 are twisted?

The standard Ethernet interface has an RC network between the centre tap of the transformer and the ground reference. What is its purpose?

Review: Balanced interfaces (Ethernet)