I was looking at an electric heater and it seems to be just some red hot wire and a fan, how can it get so hot without triggering the circuit breaker? Is it a big load? Is it something like the little filament on a lightbulb?
In: Engineering
You’re essentially right, it’s simply a wire that current runs through. How hot it gets is defined by how much current is going through it (more current = hotter, less current = cooler), which itself is a result of both the wire’s resistance and the voltage of the supply. Since the voltage from the supply isn’t going to change, the X-Factor here really is the resistance of the wire – too conductive and the electricity will just zip through and it’ll barely draw any current. Too resistant and it won’t be able to draw any current at all, like plugging a tree into a wall socket. So the amount of current it draws, and thus how hot it gets, is defined by resistance of the wire. If you know the total resistance along the length of the wire, you know the maximum current it can draw from a given wall socket and thus you know it won’t flip the breakers or blow a fuse.
This is why most commercially available heaters top out at about 2200W, as this is 10amps from a 220v AC wall socket – deliverable but below the point it’ll blow a 13A fuse or trip a circuit breaker in most cases, with a little headroom to spare to allow for varying national wall socket power, fluctuations and the possibility of other devices also being turned on.
A *short* circuit is when a connection is made between two parts of a circuit that shouldn’t be connected – maybe a metal filing has fallen onto a circuit board. This is fundamentally a different thing, because this is an example of a circuit not working as intended, where as the fan heater is just a simple circuit that also happens to be short.
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