Heres is an improvised immersion heater that was confiscated from inmates in a German prison: that looks like the absolute bare minimum immersion heater and is clearly dangerous as hell but I'm wondering how exactly it works. Its connected directly to a mains plug so there will be 240V AC current flowing through it. I see that the cord is stripped at the end, revealing a blue and a red wire. I'm guessing one wire is for current travelling down the cord (away from the plug socket) and the other wire is for carrying current back to the plug socket. The red and blue wires are then stripped and the exposed copper strands appear to connect to 3 razor blades. I don't know what that rope in the middle of the blades is for, maybe just a separator to prevent the blades from touching each other. How exactly would a device like this work? Does current travel from the red wire, into one of the razor blades, then to the 2nd razor blade, then to the 3rd razor blade then to the blue wire which carries the current back to the mains socket? Also, how exactly does this device produce heat? I know that the heat is generated by the razor blades but razor blades are made of steel or some other highly conductive alloy so I wouldn't have expected much heat to be generated when current flows through. My understanding is that resistance is required to convert electrical current into heat.