Electrical question

I've been trying to learn about ground probes and stray voltage and i get their concept but i have another question, I read that ground probe thread and one of the choices on the poll were something like: No, i dont need a ground prbe because i have a breaker or another alternative. first of all yes i do have a breaker box in my house, one time i was messing w/ an electrical project and accidentally shorted it out the powr in my room went out untill i resetted my breaker. But, if i use a wall outlet w/ a built in breaker like in the pic(just to be safer), does that mean i dont have to worry about stray voltage? Also, i know that your supposed to put the positve lead of a voltage meter in you water and the negative to a ground to measure stray voltage, but how do you ground your negative lead?

 

i think the breaker would only turn off if it starts drawing to much power or short circuits. im not a electrical person, i think there are electrical engineers on the site. i think you still could have voltage leaking and not have the breaker trip. you could ground your negative by puting it in the ground hole on your outlet(thats the whole dont stick it in the wrong one, if your unsure get your dad or mom to do it.) the ground in your socket is connected to a metal pipe that goes into the ground.