What is Capacitance: Definition and 899 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.

View More On Wikipedia.org
  1. PlanetGazer8350

    B Can ultracapacitors be used to split CO2 into carbon and oxygen?

    I have been researching on the bonding energies of different compounds, and for example, for CO2 it is 1600kJ/mole, 1600kJ/44g, or ~36.37kJ/g of energy required to split the carbon dioxide into carbon and oxygen. Furthermore, I transformed the amount of energy required in kJ to degrees celsius...
  2. Safder Aree

    How Do You Calculate the Capacitance of a Sphere Using Only Charge or Potential?

    Homework Statement Assume a conducting sphere has a radius of 3400km with an electric field of 100 V/m at it's surface. a) Calculate total charge of sphere. b)Calculate potential at the surface using infinity at reference point c) Calculate capacitance of the sphere using the result of a or b...
  3. jishnu

    Equivalent Capacitance: Find C Between A & B | Tips

    The picture attached with this post shows a combination of capacitors, we are asked to find out the equivalent capacitance between the points A and B. Provided that all the capacitors are identical and has an individual capacitance C. Can anyone help me provide basic ideas of solving these kind...
  4. J

    Equivalent capacitance in a circuit

    Homework Statement Homework EquationsThe Attempt at a Solution I think the circuit given above is incorrect due to the presence of the two resistors . I have never seen/done a problem where equivalent capacitance is to be calculated across two points in a circuit , having resistors along...
  5. J

    Capacitance and field of 2 eccentric spheres

    Homework Statement Hi there! So I have found trouble with the following problem. I have a system of two eccentric spheres, where one is inside another. The Attempt at a Solution I have found this answer: https://physics.stackexchange.com/questions/16939/capacitance-of-non-concentric-spheres...
  6. janiceyyyyyy

    Investigating Voltage, Capacitance & Resonance in DC/AC Circuits

    I have done an experimeny to investigate how the voltage across a capacitor, Vc varies as it charges and to find the capacitive time constant in a DC RC circuits and Study resonance in an AC inductor-capacitor circuit (AC LRC circuit). I am now having trouble in writing the source of error of...
  7. E

    Which quantities are not the same for this capacitor setup?

    Homework Statement Two parallel-plate capacitors with the same plate separation but different capacitance are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is NOT the same for both capacitors when they are fully charged is: A. potential difference...
  8. E

    What happens to the capacitance after increasing distance?

    Homework Statement A battery is used to charge a parallel-plate capacitor, after which it is disconnected. Then the plates are pulled apart to twice their original separation. This process will double the: A. capacitance B. surface charge density on each plate C. stored energy D. electric...
  9. D

    What is the maximum capacitance of the device?

    Homework Statement [/B] The figure [attached] below shows a variable "air gap" capacitor for manual tuning. Alternate plates are connected together; one group of plates is fixed in position, and the other group is capable of rotation. Consider a capacitor of n = 4 plates of alternating...
  10. D

    Making Capacitance the subject of discharge equation

    Homework Statement I have to rearrange the equation V=lnVo -t/RC to calculate C. The gradient from graph = -1/RC Homework EquationsThe Attempt at a Solution I got R/C=ln(Vo-V)/t but the answer I get is wrong
  11. B

    A Interface states in a PIN diode

    Is the equation used to determine the density of interface states in schottky diodes from capacitance- frequency data applicable to PIN junctions?
  12. J

    Equivalent capacitance of capacitors

    Homework Statement Homework EquationsThe Attempt at a Solution First I calculated equivalent capacitance between R and M . The two 2μF capacitors are in series . Their combination is in parallel with the 1μF capacitor . Their equivalent capacitance is 2μF . Now I found equivalent...
  13. Y

    Increasing The Capacitance In A Voltage Booster

    Good day, everyone. Let's picture a classic diagram of a voltage booster which is connected to a capacitor. If we double the capacitance, by replacing it using another capacitor with the same voltage rating as the previous one, will the circuit still be able to charge the new capacitor up to the...
  14. Z

    Two like capacitors in parallel

    I'm having a little trouble understanding capacitors in parallel and series. I understand that if there are two capacitors in a circuit with a potential difference Vab then the potential difference across the capacitors is also Vab. Every example I have seen have been for two capacitors with...
  15. V

    Dielectric inserted into a parallel plate capacitor

    Homework Statement The capacitor (of thickness d) is disconnected from a potential source of V and a dielectric of thickness t is inserted and it has relative permitivity Er. Find the new potential between the plates Homework Equations [/B] This is the answer : Vf = V/d(d - t + t/Er) The...
  16. C

    How to find the energy of capacitance?

    Homework Statement Find the energy in the 2uf capacitor in the diagram attached in uploads. Homework Equations E=(1/2)CV^2 E=QV C=Q/V Capacitor in series : 1/(Equivalent Capacitor) =Σ1/(Ci)* Capacitor in parallel: Equivalent Capacitor =∑Ci* *i is the index of summationThe Attempt at a Solution...
  17. H

    Does the charge of a capacitor change during immersion?

    If given a capacitor with stored charge, would its charge remain constant before and after it is immersed in a liquid (i.e. distilled water)? Why? I know that before immersion, the capacitance would be = (ɛAV/d), but would that be the same if immerged in distilled water?
  18. J

    Find the Capacitance when given the Power Factor

    Homework Statement w = 1 rad/s power factor is 0.8 lag Homework Equations Using Phasor we can do The Attempt at a Solution Since pf = 0.8 lag. I source lags V source by 36.87 degrees. Vc is voltage across Capacitor = Voltage across ( Resistor + inductor) Solving this I get C = 0.5 But book...
  19. L

    Line impedance versus shunt capacitance

    Hello, I'm having the damnedest time wrapping my head around a concept of audio electronics: http://whirlwindusa.com/support/tech-articles/high-and-low-impedance-signals/ How exactly does a higher impedance bring down the frequency at which capacitance dominates? My current understanding is...
  20. Javier Lopez

    What would be the capacitance of a particle on a plate?

    Homework Statement There is a charged particle at height h over a circular area of radii R, then I have to calculate the capacitance. This is useful when somebody want to calculate energy harvesting, antennas, sensors that measures ions in plasma devices and particle accelerators...
  21. J

    Capacitance of a Transmission line

    Homework Statement A single phase transmission line has 2 parallel conductors 1.5 metres apart. The diameter of each conductor being 0.5 cm. Calculate the line to neutral capacitance for a line 80 km long[/B]Homework Equations CAN = 2(3.14)(permittivity)/Loge [D/r] This gives capacitance per...
  22. reese houseknecht

    Calculating how to make a homemade capacitor

    Ok, so I am am trying to make a homemade capacitor that is 4700pf and 15kv. polyester at 125 micrometers thick can withstand 15kv so were good. here is the equation i used C=ε0 K A / D Where C = capacitance, ε0 is epsilons constant, K = dielectric constant, A = area of aluminum foil, and D is...
  23. T

    How do I calculate the capacitance of two unequal lines?

    The capacitance formula for equal line is as follows. : * my question : I want to know the capacitance formula for unequal lines and its solving process . Thanks in advance for any hint.
  24. S

    Individual Charges and voltage

    Homework Statement the capacitance of each capacitors and the cell voltage Homework EquationsThe Attempt at a Solution I got the total capacitance = 8028/5333 uF total voltage = 36v total charge=289008/5333 uC
  25. S

    Stray/Parasitic Capacitance - Impacts phase velocity?

    Hey everyone, I'm trying to measure the stray capacitance in a circuit comprised of an rf signal generator, an oscilloscope, a coaxial cable (short-circuited) and some capacitors. I measured the resonant frequencies of the coaxil cable for varying values of capacity (0pF to 850pF) between 4MHz...
  26. M

    Capacitors in Series: Intuitive Understanding Question

    I understand algebraically that when capacitors are in series, the total capacitance is less than any individual capacitance, but I do not understand this intuitively. How can this be possible? Shouldn't more capacitors equal more capacitance?
  27. M

    Capacitance and voltage relationship

    Does an increase in Capacitance mean a decrease in voltage? Thanks!
  28. J

    Inserting a conductor in a parallel-plate capacitor

    Consider a parallel plate capacitor formed by two plates of length ##L## and width ##d##, separated by a distance ##e##. There is a vacuum in between the plates. Let's note the capacitance of this arrangement ##C_0##. I insert a conducting plate of length ##l=L/2##, with ##D##, and thickness...
  29. L

    Capacitance with smoothly varying dielectric in 1D

    Dear all, I am trying to find the capacitance of a parallel plate structure that comprises a spatially varying (linear) dielectric in one dimension. I have two methods of solving this which give different answers, and I am not sure which is correct. I consider the dielectric region to be...
  30. H

    Capacitor circuit time constant problem

    Homework Statement How long does it take in time constants ( = RC) for the charge on the capacitor in the circuit shown below to reach one quarter its initial value? Homework Equations C=Q/V time constant=RC Vc = Vo * (e)^(-t/RC) The Attempt at a Solution From C=Q/V I get Q=VC so for the...
  31. mnb96

    Capacitance with changes in dielectric material

    Hello, Let's consider a capacitor simply made of two conductors with arbitrary shape in the vacuum (http://www.kshitij-iitjee.com/Study/Physics/Part4/Chapter26/3.jpg). Now, if I place a small piece of dielectric material (for example a tiny sphere of glass) between the two conductors, the...
  32. B

    Why does VFD cable data sheet show Inductance, Capacitance?

    Can someone point me to an understanding of why VFD rated cable include Inductance and Capacitance? For example, Belden cable 29504 shows impedance, inductance, capacitance between conductors, capacitance between conductor and sheild, and DC resistance. Is there a VFD motor calculation that is...
  33. RJLiberator

    Finding the Capacitance of a Conducting disc

    Homework Statement Consider a disc (negligible thickness) of radius R with its center at the origin. Assume that the disc has a radially symmetric surface charge density given by ##σ(s) = \frac{A}{\sqrt{R^2-s^2}}## at a distance s from the origin, where A is some constant. You can take it for...
  34. P

    Resistance and capacitance in LCR circuits

    Homework Statement The output voltage, V_(out) (t) ‡ q(t) /C, effectively measures the charge on the capacitor as a function of time, where q(t) is an exponentially damped simple-harmonic oscillation: a) Given that L = 0.05 mH, the square-wave frequency is 25kHz, and the ringing decays to 40%...
  35. M

    Question on corner and resonant frequencies

    Homework Statement 1. An RC filter is constructed by modifying a voltage divider. The top resistor R1 = 3kOhms remains the same but the bottom resistor R2 is replaced by a capacitor C = 8nFarads. Determine the corner frequency fc for this filter in kHertz. 2. For an RLC circuit R = 12.4...
  36. I

    Calculating capacitance from an AC circuit

    This question is from my physics book and neither I nor my teacher can find the mistake in my method. (The original question is not in English so I'll do my best translating it) > When a coffee maker is connected to the wall (230 V, 50 Hz) its power consumption is 180 W. The power consumption...
  37. M

    Question about Capacitance and Inductance

    Homework Statement [/B] Hey everyone, I recently got two problems on capacitance and inductance and need some help on them. Here are the two problems: 1. A Royal Red Robin Burger contains 1230 food calories. Also, more that the daily requirement for protein, fat, sodium ..., even without fries...
  38. L

    Magnitude of the induced magnetic field in a circuit

    Homework Statement The circuit in Fig. 32-31 consists of switch S, a 12.0 V ideal battery, a 20.0 M resistor, and an air-filled capacitor. The capacitor has parallel circular plates of radius 5.00 cm, separated by 3.00mm. At time t=0, switch S is closed to begin charging the capacitor. The...
  39. R

    Increment of capacitance of conductor

    Homework Statement A Sheet of conductor of thickness t and parallel faces of cross-sectional area >=A is inserted between the plates of the capacitor of a parallel plate conductor. Show that the capacitance increased by ΔC= ε0tA/d(d-t) Homework Equations σ,ε0,Δ The Attempt at a Solution...
  40. E

    How capacitance, charge, and energy stored changes on a capacitor?

    Homework Statement You charge a parallel-plate capacitor, remove it from the battery, and prevent the wires connected to the plates from touching each other. When you pull the plates apart to a larger separation, do the following quantities increase, decrease, or stay the same? (a) C (b) Q...
  41. E

    Equivalent capacitance and Kirchoff's laws

    Homework Statement [/B]Homework EquationsThe Attempt at a Solution I really have no idea how to proceed. Applying Kirchoff's laws to this would be quite lengthy. This circuit is supposed to be a wheatstone bridge but I can't see it.
  42. J

    Why/how does distance affect capacitance?

    As distance between two capacitor plates decreases, capacitance increases - given that the dielectric and area of the capacitor plates remain the same. So, why does this occur?
  43. J

    Inductance and Capacitance as the Secondary Load

    What are the effects of adding inductance and capacitance as secondary load of transformer? I am using a Ring /Toroid Transformer.
  44. R

    Capacitance and Dielectrics in Parallel Plate Capacitors

    Homework Statement The plates of an air filled parallel plate capacitor with a plate area of .0016 m^2 and a separation of .009 m are charged to a 145 V potential difference. After the plates are disconnected from the source, a porcelain dialectric with k = 6.5 is inserted between the plates of...
  45. S

    Calculate charge and capacitance

    Homework Statement Three capacitors are connected in series, C1 = 4.5 mF, C2 = 7.5 mF, and C3 = 10 mF, and connected to a 150V d.c. supply. Calculate: (a) the total capacitance...
  46. M

    Excess charge in capacitors connected in series

    I have a hard time comprehending excess charge in capacitor plates. Let's say we have two identical capacitor and we charged them to identical amount of charge. Next we connect them in series by opposite sign electrodes and we get double the voltage on the open ends. Now a single capacitor has...
  47. martin25p2

    Calculating the total capacitance of a network of capacitors

    Homework Statement I would like to know how to calculate the total capacity of the capacity network displayed in the uploaded picture. I know how to calculate the total capacity if the capacity are in parallel or in series, but I am confused by the capacity Nr 6. I know how to calculate the...
  48. N

    Capacitors in series or in parallel? - calculating CR

    Homework Statement I have the circuit above. When I have the switch at A, the capacitor C1 is charging at 100μF is at 10V. I then discharge the capacitor by connecting the switch to B. I was asked to calculate the time constant. I thought the capacitors were in parallel but according to...
  49. M

    Stray capacitance -- how to calculate formula....

    Hello, i am reading one book over the "tenichians radio receiver handbook", but there was a stray capacitance can somebody help me, how to calculate stray capacitance? of what arethe standard value of stray capacitance thanks. YES do you see the circuits the stray capacitance is 7pf and 320pf...
  50. A

    Why is the electric field inside the dielectric cancelling?

    So, I was studying force between the plates of a capacitor when a dielectric is inserted. Here is my question https://ibb.co/cenvXk Shouldn't it be like this picture below https://ibb.co/kOUsCk So, why is my teacher saying that the electric field inside the dielectric cancelling. So, what...
Back
Top