disconnecting the battery: negative first?

[badkuk]

bakit ung negative end ang unang inaalis, at hindi positive? di ba current flows from positive to negative/ground(which can be you)?

[yebo]

negative ang una kasi po pag accidentally nasagi mo yung wrench sa body ng car OK lang, hindi mag-short kasi negative din yung car body (- to - so no electrical flow). pag positive inuna mo at nasagi mo yung wrench sa car body e di short circuit ang labas nun (+ to -), sira paint ng car mo saka bungi na yung iyong made in germany na 12mm wrench sayang naman. ALSO, since sabi mo nga pwedeng ikaw yung "ground", hindi ka makoryente kasi negative to negative yung hawak mo (car body and negative battery terminal). imagine mo kung reverse ito, positive terminal ang hawak mo tapos grounded pa din (meaning connected pa sa negative terminal ng battery) ang car body e di electrocuted ka. (OK OK! 12 volts don't kill. but some people do get a shock from a 12 volts DC battery)

pag install naman ay reverse. positive muna. since di pa connected yung negative terminal kahit maisagi mo yung wrench sa car body wala pang electrical circuit so walang short circuit. di ka din makoryente kasi di pa connected yung negative terminal, hindika pa "grounded" kahit nakahawak ka sa car body.

"ground" is a misnomer for negative terminal so don't be confused by terminologies. there is also such a thing as "positive ground", like some old old cars.

[BoEinG_747]

bakit ung negative end ang unang inaalis, at hindi positive? di ba current flows from positive to negative/ground(which can be you)?

For safety purposes ...

just like what sir Yebo post ahead said

[Shadetree MKNX]

Whatever terminal is being grounded, that's the terminal you should mess around with first.

3 decades ago, there were still some odd makes that used "positive ground" electrical systems, and for those cars, you need to disconnect the positive battery terminal first.

It's a matter of safety *and* convenience, like the guys above said. I say "convenience" because you can actually "go against the rule" and come out none the worse from it, if you're just carefull enough--but then, why bother?

[wildthing]

OT...i think my recollection in physics says that electricity travels from the negative to the positive?!?

[yebo]

OT...i think my recollection in physics says that electricity travels from the negative to the positive?!?

flow of electrons is from negative to positive, but convention (whatever that is, must have been a group of weirdo scientists) says that imaginary "positive charges" flow from positive to negative. ang gulo nila ehehehe!

[Tacoma_34]

of course take out the negative first.

[Shadetree MKNX]

flow of electrons is from negative to positive, but convention (whatever that is, must have been a group of weirdo scientists) says that imaginary "positive charges" flow from positive to negative. ang gulo nila ehehehe!

Engineers like to think in terms of "Positron Flow", while technicians like to remain aware that it is the electrons that actually do the flowing.

The reason behind the so called "convention" is because Engineers and Scientists find it easier to deal with "positive" numbers.

Nevertheless, the question has nothing to do with how electricity flows. The main thing is to avoid that flow altogether, regarldess of what direction it takes. Obviously, un-grounding the power supply first provides that measure of safety.