1) a dead short in the circuit. Fuse will blow pretty much instantly.
2) an overload on the circuit. Fuse will blow sooner or later depending on how great the load excess is. If the fuse is rated at 3A, it's not going to be fine at 2.9A and then instantly blow at 3.1A. You'd need actual current monitoring to do that.
And some fuses are "delayed" to allow an overload for a few moments, such as when starting a motor.
None of this disputes that Amazon is well known to sell garbage, and not just limited to fuses. That's why I don't buy anything there.
1) a dead short in the circuit. Fuse will blow pretty much instantly.
2) an overload on the circuit. Fuse will blow sooner or later depending on how great the load excess is. If the fuse is rated at 3A, it's not going to be fine at 2.9A and then instantly blow at 3.1A. You'd need actual current monitoring to do that.
And some fuses are "delayed" to allow an overload for a few moments, such as when starting a motor.
None of this disputes that Amazon is well known to sell garbage, and not just limited to fuses. That's why I don't buy anything there.