Capacitor component

Capacitors store electrical charge from a power source/supply and then release that charge at a later time. The charge and discharge process is somewhat similar to that of a rechargeable battery, but there’s many differences to be aware of.

Become a Patron! Many diagrams only available to patrons.

C=Q/V – Capacitance equals electric charge divided by voltage.

Capacitors have 2 conductive areas (called plates) that are separated by a thin insulation material. Applying a voltage from a power supply to the capacitor terminals leads to charges moving out of one plate and into the other. The amount of charge needed to raise the capacitor’s voltage by one volt depends on it’s capacitance (in Farads).

The misplaced charges of a charged capacitor still want to go back to their original places. The force of which is indicated by the capacitor’s voltage. A load placed between the charged capacitor’s terminals will be powered as long as their is a charge difference between the plates. The voltage of the capacitor will drop based on how much current is being provided.

Smoothing uses

Smoothing a power supply voltage is the simplest use of a capacitor to understand. The capacitor gets charged directly from a power supply that is also powering some other load. The capacitor and the load are connected in parallel. If the supply voltage drops or spikes briefly, then a large enough value capacitor can hold the voltage much more steadily to the load.

RC time constant uses

Capacitors charge instantly if there is no resistance between them and the power supply. Current, and thus charge time, is limited by adding resistance between the power supply and the capacitor. The amount of current flow at any given time is based on the resistance and the voltage difference between the power supply and the capacitor. Therefore, there is a lot of current flow/voltage change when first charging a capacitor through a resistor, and very low current flow/voltage change when the capacitor is almost done charging to the supply voltage.

Discharging a capacitor through a resistor also has the same rapid current/voltage change at first, which slows down as it gets nearer to being fully discharge.

Multiplying the resistance by the capacitance (RC) gives the RC time constant. This is the amount of time it takes to change from the starting voltage, to about 2/3 of the final voltage. It will take that same amount of time to change 2/3 of the remaining voltage. And then the same amount time to change 2/3 of remaining voltage, and so on. Seeing as each time constant only changes 2/3 of the remaining voltage difference, the capacitor is never mathematically 100% charged. So, we settle for 5 time constants being fully charged. By that point, the capacitor’s voltage has reached a state of about 99.99% changed or discharged.


Capacitors pass AC and block DC. Often you want to let current change direction a lot (AC) in part of a circuit, while preventing it from going in just one direction (DC) for very long. You can easily do so by putting a non polarized capacitor, which can be charged in either direction, in series with the rest of that circuitry.

Links support this site:

I used capacitors from this kit in my videos, unless the value I need is not available in this kit. As an Amazon Associate I earn from qualifying purchases. Also, please subscribe to my YouTube channel!
Become a Patron! Many diagrams only available to patrons.

As an Amazon Associate I earn from qualifying purchases.

Home page

Links and disclaimer: