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When you join capacitors in series, the equivalent capacitance decreases. What are some reasons to connect capacitors in series?

user31058
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1 Answers1

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Capacitors have a maximum voltage they can take before the dielectric (or vacuum) inside of them breaks down and starts conducting. Thus, if you need to have a capacitor in a high voltage circuit it may be necessary, or just more convenient, to place them in series. Recovering the nominal capacitance of the individual capacitor, if needed, is a question of building up an array of them in parallel.

The same thing can be done with resistors when the thermal dissipation limit of the individual resistor, usually around a quarter watt, is too low.

Sean E. Lake
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  • For a given power dissipation and fixed supply voltage you put the resistors in parallel? – Farcher Apr 06 '17 at 10:10
  • Nope - you put them in series. You can either use smaller individual resistors to do this, or build up an array, as with the capacitors. The square array will have total resistance equal to the resistance of the individual resistor, and the power dissipation ability of $N$ of them. One application of this: making a battery drainer. – Sean E. Lake Apr 06 '17 at 10:12
  • Applications of battery drainers: using up the last charge in a NiCad rechargeable battery to avoid memory effect, discharging a battery before disposal to stabilize it some. – Sean E. Lake Apr 06 '17 at 10:15
  • I do not think it matters. Think of a resistor as a cylinder of resistive material. You can either "cut" the original resistor along its length which is equivalent to smaller value resistors in series or you can "cut" the original into "slices" (like from a very tall cake) along its length which is larger value resistors in parallel. The array is to be used if you have only resistors all of the same value. – Farcher Apr 06 '17 at 10:36
  • @Farcher Of course, if you can build your own custom resistors, and fiddle with the geometry to increase the surface area, that's what you'd do. Especially if you're looking to mass produce something. For one-off hobbyist items, though, making an array with off the shelf parts is perfectly reasonable. – Sean E. Lake Apr 06 '17 at 10:41