Capacitance Definition and 147 Discussions

Capacitance is the ratio of the amount of electric charge stored on a conductor to a difference in electric potential. There are two closely related notions of capacitance: self capacitance and mutual capacitance. Any object that can be electrically charged exhibits self capacitance. In this case the electric potential difference is measured between the object and ground. A material with a large self capacitance holds more electric charge at a given potential difference than one with low capacitance. The notion of mutual capacitance is particularly important for understanding the operations of the capacitor, one of the three elementary linear electronic components (along with resistors and inductors). In a typical capacitor, two conductors are used to separate electric charge, with one conductor being positively charged and the other negatively charged, but the system having a total charge of zero. The ratio in this case is the magnitude of the electric charge on either conductor and the potential difference is that measured between the two conductors.
The capacitance is a function only of the geometry of the design (e.g. area of the plates and the distance between them) and the permittivity of the dielectric material between the plates of the capacitor. For many dielectric materials, the permittivity and thus the capacitance, is independent of the potential difference between the conductors and the total charge on them.
The SI unit of capacitance is the farad (symbol: F), named after the English physicist Michael Faraday. A 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates. The reciprocal of capacitance is called elastance.

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  1. Luek

    Energy stored in a LC circuit

    Homework Statement Energy in the circuit remains constant. When the current is flowing, the energy stored is all stored in the inductor. When the current stops flowing, it is because all the energy is stored in the capacitor. Find the fraction of energy stored in the inductor when half of the...
  2. R

    Capacitance Question - Total Energy, Potential Difference

    Homework Statement Two identical parallel-plate capacitors, each with capacitance 10.0 μF, are charged to potential difference 50.0 V and then disconnected from the battery. They are then connected to each other in parallel with plates of like sign connected. Finally, the plate separation in...
  3. recursive

    Capacitor Energy With Different Dielectrics

    Homework Statement Two parallel plates are connected to a battery which maintains a constant potential difference of 12.0 V. The distance between the plates can be varied and there are three plates of different dielectric materials available: rubber (0.40 mm, κ = 6.7), glass (4 mm, κ = 7) and...
  4. E

    Dielectric in a capacitor in equilibrium

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  5. E

    Net capacitance

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  6. vetgirl1990

    Capacitance and impedence?

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  7. kostoglotov

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  8. W

    Capacitors in Series and Parallel

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  9. Phy_TR

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  10. V

    Please help me with this doubt from electrostatics

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  11. kostoglotov

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  12. A

    Self-Capacitance of an Insulating vs. Conductive Sphere

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  13. Weightofananvil

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  14. N

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  15. genxium

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  16. P

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  17. P

    Capacitance - sphere

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  18. Shreyas Shree

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  19. R

    Electricity and Magnetism RC Circuit Conceptual Questions

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  20. A

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  21. bananabandana

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  22. S

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  23. S

    Capacitance between two parallel wires not straight

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  24. F

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  25. S

    Is it possible to charge photons?

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  26. AnkurGarg

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  27. GoldWing

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  28. S

    Capacitor with magnetic dielectric

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  29. PratyashAstro

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  30. M

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  31. R

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  32. S

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  33. D

    How to switch on and off capacitance on a piece of conducting material?

    I don't know if this is the right way of describing it, but I need to activate an area of capacitance on a touchscreen by applying some current to a piece of conducting material like tinfoil. I am needing to remotely turn pages on a touchscreen ereading device with a microcontroller, and this...
  34. 1

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  35. N

    Capacitance of an asymmetrical parallel plate capacitor

    I've been looking all over and to my great surprise have not be able to find an answer to this question. What is the capacitance between to parallel plates if one plate is larger than the other? For example, the capacitance between a 1" diameter plate and a 4" diameter plate. Thanks.
  36. K

    Inserting metal to parallel plate capacitor

    If there is a parallel plate capacitor with plate area, A, plate separation, d, and a slab of copper of thickness, b, is inserted exactly halfway between the plates. How to find it's new capacitance, C', and new potential difference, V' ? Answer: V' = E(d-b) and C' = εA / (d-b) I...
  37. A

    Three plate capacitor and charge distribution

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  38. G

    Where does inductive reactance go?

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  39. D

    Testing and Troubleshooting Capacitive Sensor Probes

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  40. Hijaz Aslam

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  41. F

    Effect of capacitor plates at different angle

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  42. N

    Explanation of capacitance formula

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  43. AdityaDev

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  44. Jadaav

    Energy stored in capacitance

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  45. EnchantedEggs

    Capacitance and Electric Field

    I've gotten myself in a bit of a muddle here, I'm hoping you lovelies can help me out! So, the capacitance relates to the amount of charge a capacitor can store. Higher capacitance, greater charge. Greater stored charge, greater stored energy (right? or not?). So a higher capacitance means you...
  46. Jasonlwe

    Help please -- Model of the capacitance and dielectric

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  47. D

    Calculate the number of sodium ions entering an non-myelinated axon

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