If I have a transformer that has a 100:1 turns ratio, and the primary circuit is given 10V at 5 amps, the secondary circuit (considering no losses) would put out 1,000V @ .005A.

So my question now, if the load on the secondary circuit has a resistance of 200 Ohms, what current flows through the circuit? how do you calculate it?

 

I = E/R. That means 5 amps. Your transformer can only source 5 ma. The transformer secondary will get hot. Your load can't be larger than 200K and not overload the transformer.