MadSci Network: Engineering

Re: How do you increase the farad rating but keep the same volt. in a capacitor

Date: Sun Aug 19 20:45:39 2001
Posted By: Eric Maass, Director, semiconductors / communication products
Area of science: Engineering
ID: 998235156.Eg

Putting several capacitors in PARALLEL will increase the capacitance, measured in Farads (more commonly in microfarads, nanofarads, or picofarads). One easy way to think of this is o 
visualize a capacitor as being made of two parallel plates separated by a dielectric or insulator:

____|____      top plate
________       dielectric
        |              bottom plate

The capacitance of this capacitor is  C = Area * epsilon(0) * epsilon(dielectric) / thickness of dielectric layer

Epsilon(0) is the permittivity of free space or vacuum, while the epsilon(dielectric) is the relative permittivity of the dielectric material used.

So, the greater the area, the greater the capacitance.

If you connect two capacitors in parallel: 
____|____          ____|____
________          _________
        |                          |

Now, the capacitance will be effectively twice as much, because you have the area of both capacitors' top plates now connected on the top, and the area of both capacitors' bottom plates 
connected on the bottom.  

So, putting two capacitors in parallel is like increasing the area of the capacitors, which increases the capacitance in farads.

Here is a website from a lecture from CUNY that discusses parallel and series capacitors in more detail.

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