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

Force that holds capacitor plates

  1. Jun 30, 2010 #1
    For any capacitor, whose 2 plates or conductors are being held by a battery to a constant potential difference of V volts, there is a force of attraction between the plates, since they are oppositely charged. What is the force that 'holds' these conductors at their respective positions i.e. what is the force that maintains mechanical equilibrium of each plate?
     
  2. jcsd
  3. Jun 30, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The capacitor plates aren't just floating in mid-air. They are usually attached to a frame or the space between them is filled with some material.
     
  4. Jun 30, 2010 #3
    The dielectric slab will prevent the plates from collapsing onto each other...but what if the dielectric is air? And if the wires used to connect the conductors to the remaining circuit are weak copper strands? I am asking this because,when the net energy change for the (battery+capacitor) system is calculated when plates move nearer because of this attractive force, the total energy of the system decreases, and decrease of energy is always favourable for any system to achieve.
     
  5. Jun 30, 2010 #4
    The electrostatic force is pretty small, but yes the capacitor plates will move towards each other. Depending on inertia, friction, air movement, etc, they may or not come into contact. At the Exploratorium in San Francisco we had a big box with two thread loops hanging from the top, one a bit shorter than the other so they couldn't "collide", you could charge up the threads with the same or opposite polarities of static electricity and watch them move.
     
  6. Jul 1, 2010 #5
    Thanks a lot!!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook