Polarized and Non Pol capacitors

[Badar]

Hi.
what makes a capacitor polarized or non polarized.
Is electrolytic capacitor always a polarized capacitor?
Is polarized capacitor polarity sensitive?if so can we not attach a capacitor with an ac input without a dc offset level?
What if i connect pol capacitor to oppsite polarities of a battery?
What capacitor should i prefer in a circuit if i have polarized and non polarized capacitors of same capacitance .
NON-POLARIZED CAPACITOR IS ALWAYS OF VERY SMALL CAPACITANCE.WHEREAS POLARIZED CAPACITOR RANGES FROM MEDIUM TO HIGH RANGE.
Is this true.What are other differences.

 

[dknguyen]

A polarized capacitor will explode if you connect a voltage across it in the wrong way. Basic electrolytic caps are always polarized. There are some that are bipolar but it's just two electrolytics caps attached in reverse parallel. to each other.

The capacitor used in a circuit depends on:
-how large the capacitor is (large values only come as electrolytics)
-votlage level
-stability
-frequency response
-dielectric absorption
-cost (electrolytics are much cheaper than other types of capacitors)
-temperature
-capacitance needed
-distortion
-polarized or non-polarized
-DC offset
-a few other things that I don't quite understand

**broken link removed**

The largest values of capacitors can only come as electrolytics- and these are polarized. So non polarized capacitors are not always very small, it's just that electrolytic capacitors can be very big and just happen to be polazrised.

You must have enough DC offset for polarized capacitors so that the AC part doesn't make the voltage across the capacitor go too negative.

Seriously, you can Google all of this stuff.

 

[Hero999]

Size doesn't even come into it when we#re talking about polarised vs non-polarised.

You can get huge polarised 20V 1F capacitors for use in audio power supplys to make the bass sound louder and huge non polarised 200:mu:F 450VAC power factor correction capacitors.

 

[whiz115]

Hi.
what makes a capacitor polarized or non polarized.

the process that is responsible for the polarization is called anodizing...it is used for the creation of a thin aluminum oxide film which acts as dielectric.

Is electrolytic capacitor always a polarized capacitor?

Every electrolytic is polarized...The NP electrolytics are in fact polarized but the way they are connected
makes them NP.

unfortunately i don't know what is happening with tandalums which are also
polarized.

 

[cadstarsucks]

Hi.
what makes a capacitor polarized or non polarized.
Is electrolytic capacitor always a polarized capacitor?
Is polarized capacitor polarity sensitive?if so can we not attach a capacitor with an ac input without a dc offset level?
What if i connect pol capacitor to oppsite polarities of a battery?
What capacitor should i prefer in a circuit if i have polarized and non polarized capacitors of same capacitance .
NON-POLARIZED CAPACITOR IS ALWAYS OF VERY SMALL CAPACITANCE.WHEREAS POLARIZED CAPACITOR RANGES FROM MEDIUM TO HIGH RANGE.
Is this true.What are other differences.

Typically the electrolytic is made polarized by putting DC across it in manufacture. In non-polarized parts they put AC on it during manufacture.

Polarized parts can typically take 10-20% reverse voltage. Non-polarized ones are typically half the value for a given size and voltage.

D.

 

[Russlk]

You would be better off getting a text book at the library than asking these guys.

 

[Sceadwian]

The problem with common electrolytic caps is the oxide layer changes states when the current/voltage is reversed. Just like a battery. If reverse biased the oxide layer will suddenly start chemically reacting into a non-insulating material/state destroying the capacitors function and creating a good DC resistance which will allow massive heating/explosion. Attaching capacitors in inverse series makes them non-polar but it is limited by the devices parasitic properties. High voltage and/or currents can't be sent through inverse series electrolytic's safely.
Size is very much an issue as the oxide layer basically means the insulating layer of the cap is limited only by the deposition process limits as opposed to native material limits.