"Normal breaker connected outlets used in US houses" are already connected to ground on one side. If you grab the neutral side, you will (ideally) get no shock.

"Normal breaker connected outlets used in US houses" are already connected to ground on one side. If you grab the neutral side, you will (ideally) get no shock. If you grab the phase side then you'll complete the path to the other side, through ground. An isolating transformer is a 1:1 transformer where the input can be referenced one way and the output another. The output is not connected to ground on either side so when you grab one of the sides, that's the first time it gets referenced to ground. ...and then the explanation continues as per my previous post.