Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Separation of subatomic particles within a capacitor

  1. Jan 10, 2015 #1
    I've recently taken to understanding capacitors and capacitance. If I understand them correctly they are what store electrical charge or electrical energy. I don't quite understand their purpose though, do they keep the breadboards from overloading with power but keeping little pockets of energy? What would happen if a computer or a typical circuit board didn't have them. Also I know that a capacitor is two conductive plates with a dielectric in the middle. The electrons and protons naturally want to get to the other side of each other and align so they build up on either side of the dielectric. But how do the electrons/protons feel this pull between the other side? what is this force and what about the atoms within the dielectric why don't they react? Also if I understand this they at some point separate into two groups on either side one side being protons then other electrons so this forms something like a battery? with negative and positive terminals? why does that process allow for the storage of energy or charge so well? Also, what determines which conductive plate becomes positive and which becomes negative? It is possible I have gotten this information all wrong and that I don't understand the process.

  2. jcsd
  3. Jan 10, 2015 #2


    User Avatar
    Gold Member

    Too many questions for one post. I'll address the "I don't quite understand their purpose though,". They have a LOT of purposes. I take it that you are studying electrical components but know nothing about electrical circuits. The are used for filtering noise, for smoothing voltage in a DC voltage source that is powered from AC, for various kinds of spike coupling ... the list just goes on and on. Very few analog circuits have no capacitors.
  4. Jan 10, 2015 #3


    User Avatar
    Gold Member

    Have you done ANY web research, like the wikipedia areticle
    Or http://www.electronics-tutorials.ws/capacitor/cap_1.html

    Basically if you put a voltage across two objects (1 more positive than the other) there will be energy stored in the dielectic medium between them. That ends up being useful in many tricky ways. In the most simplistic sense it creates a tiny "battery-like-thingy".

    In a more complex applications it can interact with resistance or inductance to create frequency sensitive circuits.
  5. Jan 10, 2015 #4
    @phinds what would happen if the circuit didn't have capacitors? What do you meaning by filtering noise? smoothing voltage, like keeping the steam of voltage at continuous level so they don't get too low or too high?

  6. Jan 10, 2015 #5


    User Avatar
    Gold Member

    You are asking for a long lesson on circuits. Study up on them.
  7. Jan 10, 2015 #6


    User Avatar
    Gold Member

    That's like asking what would happen if you left out a wire in a car (except you probably understand wires). Maybe it wouldn't start, maybe the interior light wouldn't work, maybe the battery wouldn't charge. Depends on the circuit, and what the capacitor was needed for. What happens is that whatever the capacitor was doing, it doesn't get done.

    You can easily google for how capacitors filter noise, or how capacitors filter power supplies, or how capacitors tune radios, or how capacitors can block DC.
    Here is a list of applications: http://en.wikipedia.org/wiki/Capacitor#Applications

    There is no such thing as a "stream" of voltage. I know what you are asking, but you don't seem to have even a rudimentary knowledge of circuits.

    The first thing you need to understand about capacitors is how they interact with resistors. The simplest circuit is the series RC circuit, where a series resistor is used to affect the rate of change of voltage across a capacitor. But, first you need to understand ohm's law, and how resistors and voltage affect current flow.

    So, study ohm's law, and series RC circuits. When you understand RC time constants, come back and ask more questions. Or, if you really get stuck on RC time constants, come back and ask questions.

    Maybe the hydraulic model of a capacitor on the wikipedia page would give you an idea.
  8. Jan 11, 2015 #7
    Interesting and promising title of the thread! Then I read first post :(
  9. Jan 11, 2015 #8

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook