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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It’s load not voltage. If the circuit either has a leak to earth or has too much load (amps) then it’ll trip.
Technically, circuit breakers do not protect your devices. They protect the wiring itself in your walls. If your devices are pulling too much current without a breaker (or the wrong size breaker), the wires can overheat and start a fire.
It is a common misconception that circuit breakers protect your devices.
It’s not the voltage, it’s the amperage load.
Think of it like this:
I have one pinball machine. It takes 400 watts to run. Broadly speaking (I know this is wayyyyyy oversimplified), that’s 4 amps.
On a 20 amp circuit that means that I could have 5 pinball machines plugged in, each drawing 4 amps. 4×5 is 20.
The minute I add another pinball machine to the circuit, that’s 4×6, which is 24 amps. 24 is greater than 20. That load would cause the wires to heat up because they’re past the load they’re designed for, which could cause a fire. The circuit breaker recognizes that the load is too high, and cuts the connection.
A surge protector that protects your electronics goes the other way:
Your devices are designed to accept 110-120 volts. If your house gets a surge because of short or a lightning strike, too much power would suddenly try to go out of your outlet and into your electronics, which would fry. The surge protector has a circuit breaker (or fuse if it’s older) that expects 110-120 volts. If more than that suddenly comes in, it breaks the circuit to protect your devices.
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.
When you plug something into an outlet, electrons flow from the negative side of the circuit to the positive side. This flow of electrons is called an electric current. Circuit breakers are designed to protect your electronics from damage caused by too much current flowing through the wires.
Circuit breakers work by interrupting the flow of electricity when they detect a potentially dangerous amount of current. They do this by using a metal strip that melts when it gets too hot. This strip is connected to a switch that pops open when the metal strip melts, breaking the connection and stopping the flow of electricity.
While circuit breakers can save your electronics from damage, they can also cause problems if they trip too often. If a circuit breaker trips frequently, it could be a sign that there is something wrong with your electrical system and you should have it checked out by a professional.
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