Educator

Capacitor

• Capacitance: If we have 2 conductors and we place charge +Q on one and –Q on the other, a potential difference V develops, the conductor with positive charge being at a higher potential. The capacitance of this system, consisting of the two conductors, is C = Q / V.
• For a parallel plate capacitor, C = (epsilon_0) A / d, where A is the area of one of the plates (the two plates have the same area A) and d is the separation between the plates.
• If a dielectric (an insulator) with dielectric constant K fills the space between the plates of a parallel plate capacitor, then the capacitance becomes KC, where C is the capacitance in the absence of the dielectric.
• The energy stored in a capacitor is Q^2 / 2C, where Q is the charge on one plate. It is also given by (1/2) C V^2, where V is the potential difference across the plates.