meaning of postive and negative polarity symbol

Discussion in 'General Electronics Chat' started by milly molly mandy, Sep 10, 2008.

  1. milly molly mandy

    Thread Starter Member

    Sep 4, 2008
    I've just started a course in Electronics and I've been given a list of symbols to learn. One of them is a "+" meaning postive polarity. The other one is a "-" meaning negative polarity.

    I've managed to understand, if I'm not mistaken, that all "polarity" is relative, I think. That is, if one point is more positive than another, then it can be said to have positive polarity. I think that's right anyway.

    What puzzles me about these 2 symbols is:-

    Where would you see them exactly? On a circuit diagram? And if yes, you'd see them on a circuit diagram, well whereabout on the circuit diagram might you see them? And what might it mean?

    I do know that you get the "+" and "-" signs on the battery in a circuit. Do you actually see them in other parts of the circuit too?

    I hope this question isn't too complex to answer. I've learned quite a bit about beginners electronics, but I'm probably still at about level 1.

    I could just try and memorise the symbols "+" and "-" parrot fashion, but it would be nice to understand just a little of what they actually mean. Thankyou.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Yep, polarity is relative. But it lets us do things in a more uniform fashion if we agree on some common voltage reference. In the days of S. F. B. Morse, that was the earth we stand on, so the concept of "ground" and a ground reference came about. We still use that same ground in household wiring.

    In a circuit, it's only usual to see polarities marked for the power busses and electrolytic capacitor polarities. A circuit will have a common voltage measuring reference point, called ground or circuit common, and marked by the ground symbol. Everything in the circuit is positive or negative with reference to that point.

    Put a meter across a 9 volt battery. Follow the polarity markings and you will read +9 volts. Reverse the leads, and you will read -9 volts. It's all relative.
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Another use of± is to designate inputs to operational amplifiers and comparators. If the + input is more positive than the _ the output willbe positive.