Capacitors

The Capacitors calculator has equations for q=CV¹ and to calculate the effective capacitance of capacitors in series² or in parallel³.

• q - The amount of charge on either plate; each plate has charge of magnitude q (but opposite signs).
• C - This is the 'capacitance', and it's described by the equation q=CV.
• V - The magnitude of the change in potential from one plate to the other.

In casual terms, capacitors store electric energy, kind of  like a battery.  Most batteries work through chemical potential energy, but capacitors instead store energy by putting opposite charges on two plates (a positive plate and a negative plate).

q = C ⋅ V

The voltage difference across a capacitor (V) is proportional to the amount of charge (q) on each plate of the capacitor.  We write this relationship as q=CV, where where C is the "capacitance", and depends on the material and geometry of the capacitor.

The q=CV calculator tab has different variations of q=CV, just to help you with the math.

"Combining" Capacitors

Series

For an example of capacitors in series and a derivation of the following equation, please see this tutorial on electronics, specifically capacitors in series. We can describe the effective capacitance of capacitors in series with:

• `1/C_"net" = 1/C_1 + 1/C_2`

If there's more than two capacitor series, we can expand the equation like so:

• `1/C_"net" = 1/C_1 + 1/C_2 + ... + 1/C_n` where n is the number of capacitors in series.

Parallel

For an example of capacitors in series and a derivation of the following equation, please see this tutorial on electronics, specifically capacitors in parallel. We can describe the effective capacitance of capacitors in parallel with:

• `C_"net" = C_1 + C_2`

That's for just two capacitors in parallel. For more i-many capacitors, we use:

• `C_"net" = C_1 + C_2 + ... + C_i`

1. ^ Walker, Jearl, David Halliday, and Robert Resnick. "Capacitance." Fundamentals of Physics. 8E ed. Hoboken, NJ: Wiley, 2008. 657. Print.
2. ^ Walker, Jearl, David Halliday, and Robert Resnick. "Capacitance." Fundamentals of Physics. 8E ed. Hoboken, NJ: Wiley, 2008. 663. Print.
3. ^ Walker, Jearl, David Halliday, and Robert Resnick. "Capacitance." Fundamentals of Physics. 8E ed. Hoboken, NJ: Wiley, 2008. 664. Print.