I've partaken in an experiment where I am looking to create the most efficient way to conduct water electrolysis.

My only need is that I don't trip a breaker. I will be running at 120vac, and likely a 15 amp breaker.

I've been looking at resistors, and I understand the ohms aspect. I am aiming for 10 amps for the sake of saftey( I know this is still lethal, but 15 leaves no room for any other devices on the breaker), and will need a 12 ohm resistor.

I've looked up some guides on resistors, and noticed information on wattage or temperature limits. All the information on them has been very vague for me.

Can I use any 12ohm resistor for this, or does it need special specifications for my workload?

Still learning. Thank you.


Going to oxidize iron in 2 litre container. a few 6 inches between electrodes. Water is just tap water, might add salt ( 5 g/l?) to help it out. No idea how the complications of electricity work, so bear with me. Going to use copper, I know I need a larger cable though, I don't understand the width system yet, learning.

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    \$\begingroup\$ Electrolysis using AC is unlikely to work properly. \$\endgroup\$ – pjc50 Apr 13 '15 at 23:00
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    \$\begingroup\$ Please, details. Many details. What circuit? What component values? Why do you think it will work (links to the articles you're using)? How big a tank? What electrolyte? What electrode materials? \$\endgroup\$ – WhatRoughBeast Apr 13 '15 at 23:03
  • \$\begingroup\$ You seem to be planning to just stick some wires in some water with a 12Ω resistor in series (because you're assuming water has zero resistance). Is that correct? \$\endgroup\$ – Samuel Apr 13 '15 at 23:06
  • \$\begingroup\$ @Samuel I know water has a 2 ohm resistance( average tap water), and may add salt to drop it accordingly. \$\endgroup\$ – 99ytrewq911 Apr 13 '15 at 23:09
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    \$\begingroup\$ @99ytrewq911 You need DC to make the reaction work. Use a car battery and a proper control circuit, not wall power. You're far less likely to die. \$\endgroup\$ – Samuel Apr 13 '15 at 23:12

You don't need a resistor to conduct current for electrolysis. A resistor can absorb some of the ampers and voltage of the source, and make a bit of a cusion on the current.

Be careful of the amount of hydrogen and oxygen that you make as it is flammable, keep an open window.

To be efficient you need salt, that's why iron rusts faster in seawater.

A higher potential difference (voltage) applied to the cell means the cathode will have more energy to bring about reduction, and the anode will have more energy to bring about oxidation. Higher potential difference enables the electrolytic cell to oxidize or reduce energetically more "difficult" compounds. This can drastically change what products will form in a given experiment. On a practical level, both current and voltage determine what will form in a cell.

If you want to convert something nto another compound, e.g sodium chloride to chlorate, go with voltages below 12v but high currents, as they dissolve the electrodes fast.

If you want to quickly make hydrogen gas, use very high voltages like anything between 12v-80v, and bi-carb soda as an electrolyte, and also keep the electrodes spaced together within a centimeter or so, because the more water the electtriciy has to pass through, the more the water resists it, but try to use something like copper at the negative electrode, for best results, use copper sheet, because it doesn't get corroded so long as there is nothing in solution that would do so, like salt.

But what lemonie said was true and should be followed. Voltage or current alone doesn't change how much the water is electrolysed, it just changes how fast the electrodes may errode away.

You need a high wattage, the more volts and amps the better, i.e., 10 volts 5 amps is better than 100volts 100ma:

$$10\times 5=50\text{ watts}$$ $$100\times 0.1=10\text{ watts}$$

But still, I find that there is more hydrogen liberated at higher voltages. So I would recomend using 24v at the highest possible current you can get which should be roughly 18amps.

To do this, look for laptop power supplies, I know mine produces 18v at 18 amps roughly +/- 5 amps.


You need CURRENT source for electrolysis.

If you'll use 120v then several volts will be use to break H2o molecule and other hundred+ volts will just heat water or resistor.

You need low voltage source (don't know exactly how much for water, several volts) that can give lot of ampers. And also electrodes with large area

Google for electrolysis equation, mass of electrolyzed material depends on current, there is no voltage at that equation at all

  • \$\begingroup\$ Not going to use wikipedia anymore. I just saw the kJ required per mol of water. Thank you \$\endgroup\$ – 99ytrewq911 Apr 13 '15 at 23:17
  • \$\begingroup\$ Wiki says en.wikipedia.org/wiki/Electrolysis_of_water that potential of water electrolysis is about 1.23 V at 25 °C So you may try to use PC power suply 3.3v line \$\endgroup\$ – user1940679 Apr 13 '15 at 23:19
  • \$\begingroup\$ Using voltage much greater than 1.23v will be inefficient, it'll just heat water and power supply itself. More amps is better, also you need to have large electrodes to get low resistance and less power looses. Best solution would be current source, that automatically tunes it's output voltage to get specified current, but any low voltage source with lot of amps will be ok as well. Also use DC current \$\endgroup\$ – user1940679 Apr 13 '15 at 23:24
  • \$\begingroup\$ I will probably use an older ATX powersupply of mine, and use the 3.3v rail. Thank you for the help. \$\endgroup\$ – 99ytrewq911 Apr 13 '15 at 23:41
  • \$\begingroup\$ Hm, maybe using 3.3v is not very good idea, depends on how much current you need. In many ATX PSU 3.3v is made from 5v by dropping 1.7v on linear regulator. So you can use 5v, there is no big difference what o heat - linear regulator inside psu or water. Or you can find psu schematics and replace resistor in pwm controller feedback with potentiometer and get regulated power supply, then lower 5v voltage to about 2v \$\endgroup\$ – user1940679 Apr 14 '15 at 0:12

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