One of my circuit breakers (20 Amps) handles about 10 light switches in my house and nothing else. For the last couple months or so, it trips about once a week, but never in response to turning an additional light on (i.e. ~5 of the lights will be on, and then all of a sudden the breaker will trip).
Each time, I reset the breaker (without turning any of the lights off). All of the lights go back on, as they were before the breaker tripped, and the breaker doesn't trip for another week or so.
Why is the breaker tripping on its own? I would expect the breaker only to trip if I turned something on (e.g. flipped another switch) that drew more current through the circuit. In other words, if the set of lights that were on at 5pm were not enough to trip the breaker, why would they be at 6pm?
Why can I flip the breaker switch and make everything work correctly again? In other words, if some set of lights tripped the breaker at 6pm, why would the same set not trip the breaker at 6:01pm after I reset it?