A very bacis polarity question

Hello all,

I have a very very simple polarity question.

I got a device with a red and a dark grey (almost black cable), is it true that the red cable is + and the black - ?

another a little less simple question, imagine you have a typical battery charger, lets say a nokia charger, like that on the pic below:

**broken link removed**

its clear that the charger has + and -, I have no device to measure polarity, I dont even know how to do that. the question is: is the outside cord - and the inside one + ? or does it depend on the charger ? is there a "general rule" for such things ?

the reason I ask is that I have a NIMH battery pack which I need to charge, and I have a charger BUT unfortunately the little piece which comes between the charger and the battery pack is damaged and I dont know "what to connect to what".

Would it be right to connect the inside of the cord to the red cable and the outside of the cord to the black cable ?

There's no general rule - you need to measure with a multimeter to confirm which way is correct.

but I'm right about the red/black cable right in the first question, right ?

Knokke said:

but I'm right about the red/black cable right in the first question, right ?

Click to expand...

I would like to assume red is positive, but with product cheaply made in China you can't be sure of anything.

hi,
Look thru these links for the connector polarity, make sure that the charger voltage/current is suitable for your battery.!!!

nokia charger polarity - Pesquisa Google

the Nokia charger is just an example..
thanks, I will go to a place where they can tell me which side is positive and which is negative, thanks

in all my experience(which is none) outside is ground, but like they said, best to check, u dont want to fry your device just based on what iv said!

Buy a cheap multimeter and measure the polarity. That eliminates any guessing.

Here's a cheap meter that works very well for the price:

7 Function Digital Multimeter

Sometimes they are on sale for even less. They're nice because they won't break the bank if they get dropped or otherwise ruined. There is at least one other meter similar to this one at a similar price available from Harbor Fright. This one is the model 80899 and is the preferred one.

With the meter on the 20 volt DC (direct current) setting and if the red (+) probe tip is in contact with a positive voltage wire or terminal the meter will display the voltage present. If the polarity is reversed and the red probe tip is on a negative wire or terminal, a minus sign will precede the voltage reading. You can experiment with a 9 volt battery to see this. Automobiles are DC devices. AC (alternating current) such as what's in your house wiring does not have a polarity so probe colors won't matter.