# Fuses AC/DC high/low V?

Discussion in 'General Electronics Chat' started by anode505, Feb 2, 2011.

1. ### anode505 Thread Starter Member

Apr 21, 2009
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Kinda a dumb Q, but with the standard glass fuses that all seem to be rated at 250VAC and x-A

Does it matter?
Does Ohms law factor in?
I have seen specs on 'things' (not fuses per say) that will state (for argument) 10amps AC, 5 amps DC at the same voltage rating.

They are basically a thermal device too much heat (watts?) and they melt, no?

(I'm feel I'm thinking about it too much its round, it rolls its a wheel. )

Dec 26, 2010
2,147
300
It is not clear what you are asking here - are you referring to the fuse voltage rating? This does matter a great deal, but is not really a function of ohms' law.

The voltage rating indicates the (maximum) circuit voltage that the fuse is able to break. Using a fuse in a circuit operating above its rated voltage may result in failure to interrupt the current safely when the fuse melts. For instance, an arc might persist within the fuse, and its body might melt or burst.

3. ### anode505 Thread Starter Member

Apr 21, 2009
12
0
I'm talking mainly below the voltage. A 250VAC 250ma fuse will still blow at 250ma at 24VDC?

Kinda my point is the melting is from watts/heat no? So do fuses need to be de-rated for lower voltage?
(that should have been my OP)

4. ### beenthere Retired Moderator

Apr 20, 2004
15,815
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It may open, but using a fuse with a 32 volt rating (generally for automotive usage) will guarantee the element will completely open up.

5. ### marshallf3 Well-Known Member

Jul 26, 2010
2,358
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It's all a matter of how wide the fuse opens up when it blows. 120VAC through a 32V car fuse may arc.