The breaker is drawn cut open and larger than life. Real parts are shaped and placed differently by each maker.
Amber dots show how much current flows. Red diamonds show fault current. They do not show electron speed. Real electrons drift less than a millimeter a second.
On the overload tab, time runs faster. On the fault tabs, time runs 150 times slower, so you can see the AC current swing back and forth. The clock shows real time.
An overload means a sound circuit is asked to carry more load than it is rated for. A short circuit and a ground fault are faults, a different problem, Article 100.
Trip times come from a teaching model, not one product. The model stays on at 20 A and trips within the UL 489 test limit of one hour at 135 percent. Real trip curves are wide bands, so check the maker's curve.
A real breaker may take minutes to trip at one and a half times its rating. The strip in this picture trips on the fast side.
In the model, the strip trips above 125 percent of the rating. Below that, a breaker can carry a little too much for a long time. That is why the wire must suit the breaker.
In the picture, the magnet trips the breaker at 200 A, about 10 times the rating. It opens the contacts in one cycle. These are typical values.
The fault current counts only the resistance of 50 feet of 12 AWG copper. That wire has 1.93 Ω per 1,000 feet, Chapter 9, Table 8. The service and the utility transformer add more resistance, so a real fault draws somewhat less current. The picture shows a solid fault.
12 AWG copper may have a 20 A breaker, 240.4(D)(6). The ground wire is 12 AWG too, the size Table 250.122 gives for 20 A.
Fault current must have a low-resistance path back to the source, 250.4(A)(5). The earth is not that path, 250.4(A)(5)(c). So the ground rod carries no fault current.
This is the service panel. The main bonding jumper ties the neutral bar to the panel and the ground bar. The wire to the ground rod lands on the neutral bar.
To fix a nick, the electrician turns the breaker off, tests the wire dead, cuts it back past the damage, and strips it again. At least 6 inches of free wire must stay in the box, 300.16(A).
The strip turns red as it heats. A real strip does not glow.
Most dwelling rooms also need AFCI protection, 210.12(B). The picture shows a plain breaker.