I know it may be sounds silly! But I can not figure out where from it comes - the second half-wave (let's say positive) in full-wave rectification. Is there any key to understand it? I mean: there is only one cycle at a time, and we currently see it's positive half, but when the cycle going down to minus V, where from the second positive half-wave appears?
I may guess where it comes from in the case of two secondary windings with common center where the signal of the second coil acts in anti phase 180° (I'am right?). But when there is only 1 secondary winding, what is the trick to double the frequency?