I have some very basic understanding of current, voltage, resistance and that circuit breakers have fuses which blow if a current threshold is surpassed. But I don’t understand how putting multiple devices connected to your wall outlets, especially if they’re connected to the same fuse, would trigger this. Isn’t the voltage allocated to each circuit the same?
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There are currently 3 types of circuit breakers commonly used in the US at least (not sure about other places).
The first is a just checks the amperage (the overall flow of electricity) to keep it below a certain threshold. Too high an amperage can cause failure in things like wires and connections, cause them to overheat and melt, or start a fire. In the US the most common allowance residential amperage is 20amps and you will have multiple 20A rated devices (like receptacles) connected via 20amp rated wires back to 20 amp rated circuit breaker. These types of circuit breaks are slow to react so it takes around a second for them to detect the overflow and cut off the circuit. Ideally, these breaks saver the user from overloading a circuit, like if they had 20 receptacles all on one circuit and all being used for high-draw devices. These are a bit “old fashioned” in modern building codes, as I’ll explain in a moment.
The second type is called a “GFCI” or “Ground Fault Circuit Interrupter”. Flowing electricity creates a magnetic field around it, since most wires have two conductors within them, with electricity flowing one way in one wire and the exact opposite way in the other wire the magnetic fields usually cancel out perfectly. But in the event of a “Ground Fault” – meaning electricity is going somewhere else, for example a hair drying dropped in a bathtub is shorting out and sending electricity into the water – the flow of electricity is imbalanced. GFCIs detect this extremely quickly and cut the circuit. These breakers can both be installed in your main panel, but also local to the devices and receptacles. These are those boxes with the two buttons “test” and “reset”. By code you need these on receptacles and devices that are likely to be used near water, like bathrooms or kitchen sinks.
Finally, the newest type you’ll see in residential circuiting are called “Arc Flash breakers”. These function like the old fashioned circuit breakers above but react in a fraction of a second. These are looking for sudden faults in wiring that cause electricity to bypass the load (the device it’s powering) and jump instantly from high to low voltage, for example if you just grabbed two exposed wires and just smashed them together in your hands. These protect the user from things like worn wires, old and damaged devices, or other fire and electrocution hazards. Unfortunately devices with electric motors like vacuums or even the fans and power supplies in computers naturally trigger a fast spike in draw when they engage so if you keep getting a blown circuit every time you want to vacuum your living room or when your GPU engages with a video game, it’s probably an over-zealous arc flash breaker.
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