Javascript® Electronic Notebook Basic Capacitors by Martin E. Meserve

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The equations for calculating capacitors in Series is on the left. You might note that this is similar to resistors in Parallel. Capacitors in Parallel are simply added together (see the section below), whereas capacitors in Series require a more complicated equation.

The resultant of two, or more, capacitors in Series can be calculated using the equations on the left. With only two capacitors in Series, the upper equation can be used to determine the total capacitance. For three, or more, capacitors, the lower equation needs to be used.

Enter your capacitor values at the top of the diagram, under C_{1}, C_{2}, and C_{3}, and then click outside the box to find C_{T} for the capacitors in Series. If you only wish to calculate the resultant value of two capacitors, leave one of the boxes empty or enter 0.

On the left is the equation for capacitors in parallel. The total, C_{T}, is the sum of all the values in parallel. The drawing to the right can be used to illustrate that fact.

In the areas provided, enter your capacitor values for C_{1}, C_{2}, and C_{3}, and then click outside the box, to find C_{T} for the capacitors in Parallel. If you only wish to calculate the resultant value of two capacitors, leave one of the boxes empty or enter 0.

The resultant value is always less than the lowest capacitor.

If the capacitors are of equal value, the resultant value is equal to the value of one of the capacitors, divided by the number of capacitors. For example, if there are three 100 pF capacitors in series the resultant value will be 100/3 = 33.333 pF.

If a very large capacitor and a very small capacitor are in series, the resultant value will only be a little bit less then the smaller capacitor. For example, if there are a 10,000 pF capacitor in parallel with a 100 pF capacitor the resultant value will be 99 pF. Just 1 pF less than the lower value resistor.

Note: There are many instances of having small capacitors in parallel with large ones. Most commonly, this is seen in power supplies. This is done to exploite the physical properties of the different capacitor types, rather than adjust the value.