How to tell polarized from non polarized capacitor

Thread Starter

Then along came a dummy

Joined Jun 24, 2005
Hello there,

I'm very new to electronics and am teaching myself. i went to radioshack to buy supplies. This may sound stupid but how can you tell if a capacitor is polarized or not. Sometimes the capacitors are labeled as such sometimes not. The radioshack guy knew nothing but how to work the register.

Are certain metals polarized (like tantalum)? What about when it says electrolytic?

Any help is truly appreciated.


Joined Apr 20, 2004

The folks at Rad Shack aren't too informed, are they?

Most often, if the capacitor has a tubular body, it is going to be polarized. All tantalum caps are, without exception. There are exceptions, but you probably won't find them at the Shack. Electrolytics have the negative lead marked, usually with arrows and "-" signs. Tantalums have the positive lead marked.

If the cap is ceramic, monolithic, film, polyester, or silver mica, it will not be polarized. Watch working voltage, though. Any capacitor will fail if too much voltage is placed across it.


Joined Jan 18, 2005
The radioshack guy knew nothing but how to work the register.
HA HA HA - - - I love it! - - - and what do their commercials say? "If you've got questions, we've got answers!" - - - WHAT A HOOT!

The only answers you'll find there are about cell phone plans. Most radio shacks have "crossed over" into the cell phone demension.

I could'nt resist to throw that in. Anyway, looks like Beenthere's gotcha covered.


Joined Jun 25, 2005
We used to have radio shack in the uk, it was called tandies, they used to know their stuff, and be very friendly (often giving me free stuff when I was little).
Sadly in their later years, they stocked less and less in the way of electrical components, and their knowledge levels dropped sharply with all the "new" staff they got in.

I remember going in and asking for a replacement bit for my soldering iron, the assistant looked at me as though I was stupid and said certainly sir, which bit of the iron would you like...................


Joined Jun 12, 2005
Originally posted by Then along came a dummy@Jun 25 2005, 03:36 PM
Thanks guys! Really appreciate the feedback as i have pretty much been flying solo so far.
[post=8716]Quoted post[/post]​
A non-polorized capacitor will have no + or - markings on it. It will also have the letters NP. Any kind of capacitor you need can be obtained from Newark electronics, Allied or many others.