It's a good many decades since I last did this kind of thing in anger, and I've been trying to find the actual equations that will back up my instinctive response, but have not yet found it.

Since, as far as I can see, both sides of your transformer are equal (i.e. same number of turns, same field strength), thus there will not be any adjustment in impedance from one side of the circuit to the other, so I would expect peek power to be when the impedance on both sides match (i.e. both sides with 5 ohms impedance).

As I say, I have not yet been able to find the equations that will back that up – but then, I can't see how it could be anything else, since there is no step-up or step-down through the transformer.

**G***eorge*