Now, lets go back to the part we skipped before about which direction things get hooked up. For a light bulb it doesn't matter which way it is hooked up, it will work both ways so in this example we do not have to worry about it. In most circuits you do have to think about the way that certain parts go.

This is the concept of polarity. The terminals or legs of a device are frequently marked with a (+) and sometimes a (-). The (+) side is called the positive leg, or is said to have positive polarity, while the (-) side is called the negative leg, and has negative polarity. You can just say positive and negative if you like, most people do.

Lets take a close look at the 9V battery we've been using and see if we can figure out which leg is positive.

See how the small terminal has a + sign pointing to it? That's the positive leg. To represent this particular leg we put a + sign in the schematic on the appropriate side of the battery. Take a look at how this looks. We'll reshow all 3 previous schematics with the polarity added.

Notice that in these pictures we have properly designated the positive terminal of the battery. It still doesn't matter how we hook it up because we are just hooking it up to a light bulb, which doesn't care about polarity.