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Obviously metal plates don't care about polarity as they are almost identical and so can be interchanged without anyone noticing a difference. | Obviously metal plates don't care about polarity as they are almost identical and so can be interchanged without anyone noticing a difference. | ||
These were pretty large capacitors | These plate capacitors were physically pretty large capacitors but their capacitance is pretty low. | ||
To save space and increase capacitance the 2 plates can be made of metal foil and the air can be replaced by an electrically insulating layer | To save space and increase capacitance the 2 plates can be made of metal foil and the air can be replaced by an electrically insulating layer in between. To save even more space the foils can be rolled into a tube. ([http://wiki.4hv.org/index.php/Rolled_foil_capacitor_-_60_kV,_3.5_nF Insctruction] to create your own capacitor of foil) This cylindric form of foil capacitors was very common for a long time -but nowadays foil capacitors are mainly rectangularly shaped blocks. There are still few current foil capacitors which are cylindrical - but most of today's cylindrical capacitors are of an other kind (the elctrolytic capacitor, see next section about polarized capacitors). | ||
An other type of an unpolarized capacitor is the ceramic capacitor. Here the plates are insulated by ceramics instead of foil - increasing the capacity and maximum voltage rating. [http://en.wikipedia.org/wiki/Ceramic_capacitor Images on wikipedia] | An other type of an unpolarized capacitor is the ceramic capacitor. Here the plates are insulated by ceramics instead of foil - increasing the capacity and maximum voltage rating. [http://en.wikipedia.org/wiki/Ceramic_capacitor Images on wikipedia] |
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