Output voltage from mains driver?

[A_Camera]

Solenoids take more current if you load the plunger, as you disrupt the magnetic field. The essential law of physics, that you don't get anything for nothing, applies.

Yes, that was my argument also, but since I have not measured it, for me that's just based on logical thinking and what I also learned a long time ago. Never the less, I won't argue further with him about it, so I dropped that question. Also since measuring the current is not that easy with my instruments, it is not easy to present a proof so for now, moving in air will do but yes, I expect some significant current increase if I'd measure under load.

If I had the time, I'd built a dynamometer to run some tests. I have the plans for one, just not the time.

Well, time is ALWAYS a constraint. If we do something boring then the time never ends and a minute might feel like an hour, if we have fun the time is over before we know it and an hour might feel like a minute... :)