Capacitors

• Coulomb's law


  The magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them
• Electric field


  The electric force on a charged body is exerted by the electric field created by the other charged bodies
• Gauss's law


  The total electric flux through any closed surface is proportional to the total electric charge inside the surface, divided by ε0
• Electric potential


  The potential energy per unit charge that is associated with a test charge
• Capacitor


  A device that stores electric potential energy and electric charge

  
• Types of capacitors

  • Electrolytic capacitor
• Capacitance in Parallel-Plate Capacitor


  • Formed with two conductors separated by an insulator (or a vacuum)

  
• Initially, a capacitor has zero net charge
• Charging a capacitor


  1. Electrons are transferred from one conductor to the other

  2. Capacitor is attached to a battery

  3. Capacitor is disconnected when at higher potential, +Q is established

  4. At lower potential, -Q is established

  5. Equal number of oppositely charged charges in each terminal, resulting in zero net charge

  
• Potential difference of a capacitor


  The difference between the higher and lower potentials, equal to the voltage of a battery when the capacitor is fully charged
• Capacitance


  The measure of the ability of a capacitor to store energy

  
• The greater the capacitance, the greater the charge on each conductor for a given potential difference, and the greater the amount of energy that is stored
• Parallel-plate capacitor


  An ideal model of a capacitor with two parallel conducting plates separated by a distance

  
• Parallel-plate capacitor

  • Uniform electric fields localized in the region between the conducting plates
  • Charges on each plate are uniformly distributed over the surfaces

  
• The capacitance of a parallel-plate capacitor depends only on the geometry, being directly proportional to the area of each plate and inversely proportional to the distance between the conductors