What's the polarity of this capacitor?

Question

Please, help me to determine the polarity of a RWA1C101MEG capacitor. I see a fat stripe on one side of the capacitor:

Is this a positive or negative terminal?

Answer 1

On those little plastic rectangle surface mount packages, which are most common for Tantalum capacitors from what I've seen, the grey/white stripe on the end of the package indicates the POSITIVE terminal of the capacitor.

In the metal "can" style capacitors, and the usual plastic/polymer round cylinder style packages the marking is usually for the NEGATIVE terminal. The tall round cylinder packages often have a grey-ish stripe, with obvious black minus signs going down it. On the metal can packages, the negative terminal is usually indicated by a solid black semi-circle/area of the circle closest to the pin, on the top of the case.

This is from experience, using products with more useful datasheets that specifically mention the polarity markings - and then it's just an industry standard that you'll see throughout your time designing stuff.

Answer 2

I have found some capacitors like orange drop or green or brown ones to be labeled wrong. The way I find out which is the correct polarity is to cut a 2 ft length of shielded cable and place a mono headphone jack on both ends. plug one end into an amplifier with the volume control set to mid way. Then touch the leads of the capacitor making sure one side touches the tip and the other side touching the stem of the jack. Holding the capacitor make note of the hum. The hum will always be louder when the capacitor is positioned with the supposedly negative side touching the tip of the jack. if you reverse it the noise will lessen so now the lead on the tip is positive and the lead on the stem of the jack is negative