WSM Posted May 31, 2015 Posted May 31, 2015 Lower voltage(with same resistance) mean lower current and the other way around Yes. Ohm's law is E over I times R. That means I times R equals E, E divided by R equals I, and E divided by I equals R (they're all inter-related). Also part of Ohm's law is P (power measured in watts) over I times E, and it works the same way as E over I times R. For example, if you have a 60W lamp powered by 120Vac, according to Ohm's law, the current demand is 0.5A. If you have an LED lamp that uses 0.05A and run it on a 120Vac circuit the actual power demand is 6 Watts (regardless of the light output equivalency). Once you understand the simple algebra involved, it's a very useful tool. WSM
WSM Posted May 31, 2015 Posted May 31, 2015 Anything can be bought for enough money! BUT when price is the only driver then people usually re-purpose something less than optimally suitable. Hence the laptop psu with a length of thin wire so that the current causes to voltage to drop to a useful value. Probably the most critical detail is the ripple voltage. Trying to get good current flow always runs close to getting some ripple peaks causing electrode erosion. Ripple can be removed by a good filter. The better DC power supplies have a Pi filter in the output circuitry which greatly diminishes the ripple (if not removing it entirely). The RC components of the Pi filter delay the rise and dip elements of the ripple, "smoothing" it to very much nearer the ideal flat DC line we need for optimal electrode efficiency. WSM
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