Ohms law really doesn't apply*. At normal current levels a fuse is much more a wire than a resistor. If a fuse ever measures at 2+ ohms it's a bad fuse.
TLDR:
Current blows fuses**.
Voltage is important for arcing as explained above.
Fuses should (may) have different max voltage ratings for DC vs AC because of the arcing issue and some may be specific for AC or DC.
Fuses used on boats should be ignition protected, particularly for high loads.
The purpose of the fuse is to protect the wire - i.e. the fuse burns inside it's protected case before the wire burns inside that nice wooden cabinetry which may cause a bad day on the water.
* Well, reeee, yes, ohm's law always applies somehow, someway. But not to calculate anything about fuses from a user's perspective. Nobody really needs to care about all that except for the person designing the fuse.
** Really it's current + time. But we don't really care that much because the wire that's being protected also has a time factor before it bursts into flame, and that time should be greater than the fuse if the wire and fuse was sized correctly. Example, how a Blue Seas MBRF fuse reacts to current over time:
So, for minor overcurrent situations, it could take quite awhile to pop this fuse.
This is why MBRF's and other large fuses are perfectly acceptable to be used on batteries that provide starting power to boat engines. (There's a MaineSail article on this)
www.electricaltechnology.org
