How does an isolated ground prevent ground loops? Whats the science behind it?

Question

How does an isolated ground prevent ground loops? Whats the science behind it?

Can anyone answer this in a manner as if speaking to someone with zero electrical engineering experience?

Answer 1

current wants to flow through any path with a low impedance (that's kind-of-like resistance). Sometimes you don't want current to be able to flow for reasons of noise, radio emissions or whatever. Isolating the grounds prevents a path (a "loop") for this current.

Answer 2

Most wiring in the US has the ground tied in with the neutral. The neutral provides a path of least resistance for current to return to earth (because it's usually tied in with the ground).

A ground fault circuit interruptor works because it measures the difference in current between the neutral and the ground. (You need an isolated ground in order to hook up a GFCI.)

How does it work? Let's say you drop your curling iron into the bathtub. It travels the path of the copper plumbing to the earth. It has 20 ohms resistance. You have created a situation that is drawing 6 amps (Ohm's law: 120V / 20 ohms = 6 amps). If you have a 15 amp breaker, the breaker never trips because the current draw isn't high enough as it electrocutes you.

With a GFCI, the neutral will have a 6 amp current on it, the ground will have nothing, and the GFCI breaker trips, possibly saving your life.

I hope I explained the science well enough using a real world example without getting too technical.