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Where to put fuses in a dc circuit?

Say I have a 12 volt battery and I want to connect a light and a radio.  Should I put a fuse next to the positive or negative terminal of the battery?  Or should I fuses in front of everything.  DC current flows from pos to neg right?  so I would put the appropriate fuse on the positive side of each electronic device?    

9 Replies

Dr.Bill (author)2010-10-30

All my equipment is fused individually on the positive (red) wire.
If you want to fuse the Positive side wire off the battery too its OK.

frollard (author)2010-10-25

Seconded. It will work on either side, but in series with + is most common.

"current flows from pos to neg right?" -- Depends, current 'technically' flows from - to + (electronis are negative, and they are the part that moves). In the old days it was thought that there was a positive particle that moved so "conventional current" is + to -. These days many schematics use the same old symbols that indicate the direction of conventional current (transistors, diodes, etc) but it's important to understand the difference.

Jason_Knighte (author)frollard2014-01-08

That is good to know man. Thanks for the help I was wandering the same thing, and its working, so I am happy with it.


steveastrouk (author)frollard2010-10-26

Tut tut. Are you talking about majority or minority carriers ?Conduction in solid metals is by electron flow sure, but not for a lot of other things.



NachoMahma (author)2010-10-26

. Is fusing the positive side a standard (a Q&D search didn't turn anything up) or just convention?

frollard (author)NachoMahma2010-10-26

Every fuse I've seen has been on the hot side of AC, or non-ground side of a DC circuit. Probably just convention.

seandogue (author)NachoMahma2010-10-26

Do whatever you like.

orksecurity (author)2010-10-25

Fuse goes in series with the load, to protect the power supply if the load shorts out. Positive or negative side doesn't matter; fuse responds to excessive current, not voltage or polarity.

Re-design (author)2010-10-25

In a circuit like this it doesn't matter.