The discussion centers around the effects of manipulating the surface area of foil on capacitance, particularly in homemade capacitors. Participants explore the implications of crumpling foil, etching surfaces, and the properties of different materials used in capacitors, including ceramics and films.
Participants express a range of views on the effects of surface area manipulation on capacitance, with no consensus on the best methods or outcomes. Some agree on the importance of uniformity in capacitor design, while others debate the implications of surface roughness and etching.
Participants mention various factors that could influence capacitance, including the dielectric thickness relative to surface irregularities and the potential for internal shorts in homemade capacitors. There are also references to the complexities of capacitor design that may not be easily addressed in a home setting.
This discussion may be of interest to hobbyists and researchers involved in capacitor design, materials science, and experimental physics, particularly those exploring homemade capacitor construction and the effects of surface area on electrical properties.
Samson4 said:Well I mean the conductors, not the dielectrics. Film capacitors are metalized so that might be hard to do. But ceramics have solid electrodes I believe. Why don't they increase their surface area?
Wow! that's great ! and i think its really fun doing that indeed.Samson4 said:To increase the capacitance of my homemade caps. A lot of the things I'm doing needs very specific specs that I don't find available. Also, I enjoy making them.
Bystander said:You're looking at the volume of the dielectric, its surface area times thickness, not a fractal surface area of the plates when calculating capacitance.
Joseph Austin said:un doing that indeed.
I suggest use foil as an alternative capacitance for your homemade c
It is not manipulable in the sense you want. If the dielectric spacing is small compared to the scale of the surface irregularities, and you can "nest" your enhanced surface area plates like cupcake pans, it's worth the effort. Scaling each layer differently to roll sheets of cupcake pans isn't worth the engineering and fabrication headaches.Samson4 said:Is it no manipulable?
Electrolytics aren't really capacitors --- they're batteries with low capacities and high discharge rates, and electrode surface area does make a difference.Samson4 said:Why do they etch the aluminium in electrolytic capacitors?
If you just make the surface of the electrodes 'rough' you may be increasing the area but you are also increasing the spacing between some parts of them and that must decrease the overall capacitance, I think. If you make 'spikes' then you would need to produce matching spikes in dielectric and the other plate, which would be difficult - especially at home because of the possible tolerances. The clever thing about good conventional capacitor design is to make the spacing and dielectric thickness as uniform as possible because it is the point of least separation that determines the maximum operating voltage.Samson4 said:Im more interested in very small imperfections. For example, if I etch my foil with hcl, will this increase the capacitance?
sophiecentaur said:If you just make the surface of the electrodes 'rough' you may be increasing the area but you are also increasing the spacing between some parts of them and that must decrease the overall capacitance, I think. If you make 'spikes' then you would need to produce matching spikes in dielectric and the other plate, which would be difficult - especially at home because of the possible tolerances. The clever thing about good conventional capacitor design is to make the spacing and dielectric thickness as uniform as possible because it is the point of least separation that determines the maximum operating voltage.
If you want to make good home made (tubular) Capacitors then you need very flat foil with no burrs on the cut edges and a very uniform thickness dielectric. Also, you have to wind them (Swiss Roll construction) uniformly tightly and exclude any dust or dirt. I have given students the task of producing Capacitors for a homework task and they mostly are just not careful enough to get good results - internal shorts are very common. If you are very careful, though, you should be able to achieve something worth while. Good luck.