What is Dielectric: Definition and 729 Discussions

In electromagnetism, a dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, but instead only slightly shift from their average equilibrium positions, causing dielectric polarization. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field (for example, if the field is moving parallel to the positive x axis, the negative charges will shift in the negative x direction). This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field.The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important for explaining various phenomena in electronics, optics, solid-state physics, and cell biophysics.

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  1. J

    Electrostatic discharge without dielectric breakdown?

    I saw an experiment the other day, where a van de graaf generator charges up this big smooth chrome sphere. There is a "wand" with a much smaller sphere nearby that's grounded, and periodically a spark can be heard and seen when the big sphere dischrages to the wand, which corresponds to...
  2. gracy

    Is dielectric necessary in capacitors?

    Why do capacitors need dielectrics (insulators) in between the two plates(conductors)?What if there is no dielectric in capacitors ?Function of a capacitor is " a capacitor stores energy in the form of an electrostatic field between its plates" Let's say there is a conductor is between them...
  3. C

    How does a dielectric affect the capacitance of a capacitor?

    Homework Statement Homework EquationsThe Attempt at a Solution for #14, I remember a battery maintains the potential therefore, V should be constant; dielectric increases charge on plates and increases capacitance but I couldn't find an option that matched. The answer key says "d" but I...
  4. sergiokapone

    Сurrent through spherical capacitor

    Homework Statement Determine the conductivity of the insulator in a spherical capacitor filled with weakly conductive dielectric. Specific conductivity of the dielectric is λ, the dielectric permittivity ε. Ansver in book is ##\Lambda = \frac{4\pi\lambda}{\epsilon} \frac{R_1R_2}{R_1-R_2}##...
  5. phys-student

    Energy of 2 spherical shells filled with dielectric

    Homework Statement 2 concentric conducting spherical shells, with radii a and 2a, have charge +Q and -Q respectively. The space between the shells is filled with a linear dielectric with permittivity ε(r) = (ε0*a)/(1.5*a - 0.5*r), which varies with distance r. a) Use Gauss's law to determine...
  6. N

    Capacitors in a series circuit W/ one dielectric

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  7. E

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  8. I

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  9. P

    Electric Fields in Coaxial Cables: Understanding Bound Charge Densities

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  10. yango_17

    Realistic Capacitor with leaking dielectric

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  11. xSpartanCx

    Building a capacitor to find the dielectric constant

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  12. U

    Dielectric material in 'induced electric field'

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  13. P

    Dielectric inserted in parallel plate capacitor

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  14. C

    Capacitor Charge Calculation with Dielectric Insertion

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  15. pangru

    Dielectric confinement effect

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  16. P

    Capacitor Questions (Voltage and Dielectric)

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  17. T

    Capacitors and Dielectric Oil: Calculating Electric Displacement and Field

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  18. Benevito

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  19. S

    Electrical Can I Use JB Weld to Build DIY High Voltage Vacuum Feedthroughs?

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  20. sergiokapone

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  21. T

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  22. bananabandana

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  23. roms05

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  24. F

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  25. B

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  26. I

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    Homework Statement What is the magnitude of the electric field due to a 6.0 x 10-9 C charge at a point located 0.025m from the charge? The charge and the point in question are located underwater (κ(water) = 80). Homework Equations I know that E = magnitude of electric field = kq/r2, where k =...
  27. Quotes

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  28. W

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  29. H

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  30. N

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  31. L

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  32. T

    Can ponderomotive force induce motion in neutral gas?

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  33. Robsta

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  34. gracy

    Plates of capacitors and dielectric constant

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  35. M

    Capacitor's dielectric and voltage?

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  36. R

    Dielectric Cylinder Polarization (Electrostatics)

    Homework Statement An infinitely long dielectric cylinder with radius R and relative permittivity ##\epsilon_r## contains a free charge density given by: ##\rho(s)= ks## for s<R and 0 for s>R, where k is a constant. Find the polarization P and any volume or surface polarization charge...
  37. B

    Removing The Dielectric From A Parallel Plate Capacitor

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  38. B

    Need help proving an equation for power loss in a dielectric

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  39. T

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  40. S

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    Odd question, would anybody know what would happen if a parallel plate capacitor (good conductor) had a soft magnetic material (fairly poor conductor) as a dielectric? What would be the DC/AC electrical characteristics of this?
  41. N

    Cylindrical Charge distribution with dielectric shell

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  42. samjohnny

    Capacitor and Dielectric: Calculating Electric Fields and Stored Energy

    Homework Statement A parallel plate capacitor with plate area A = 100 cm^2 and plate separation of d = 5mm is connected to a 120 Volt power supply and allowed to fully charge. a) Calculate the capacitance, stored charge, electric field midway between the plates and potential energy stored...
  43. O

    Dielectric effects confined inside the dielectric material?

    Hi all, I am wondering how is it possible that the polarization effects of a dielectric material remain confined inside the material itself. That is: for a LIH dielectric, the equations state that the electric field inside the material is reduced by \epsilon_r. But outside the material, no...
  44. R

    Inserting Dielectric into a capacitor in parallel

    Homework Statement Two identical capacitors Ca and Cb each of capacitance 6.60 http://lon-capa.mines.edu/adm/jsMath/fonts/cmmi10/alpha/100/char16.png F are connected in parallel across a CONSTANT total electric potential difference of 480 V. A dielectric slab of dielectric constant 4.65 can...
  45. B

    How to calculate value (kg) material?

    Hi I have a the problems! i need this materials for dielectric : 1.pvc (Kg) 2.dop (Kg) 3.carbonate (kG) so, i Specify this propertise for dielectric : 1.T(Tensile strength) =16 2.E(elongation) =300 3.Density=1.45 4. H(Hardness)=78 now, I need to...
  46. Symmetry777

    Dielectric Constant Chart of Gases

    Is there a creditable chart out there - on the dielectric constant of gases? What is the dielectric constant of Sulfur hexafluoride (SF6) compared to other gases or other gases in a vacuum? Thank You
  47. P

    What Happens to a Partially Inserted Dielectric in a Capacitor?

    1. The problem statement, Dielectric plate is placed in capacitor to the half(picture) and it can freely move. Capacitor consists of two parallel plates and is isolated. Consider two cases: a)charges on plates are constant, b)voltage is constant. What happens in each case? 2. Homework...
  48. S

    Does a capacitor have to have a dielectric?

    Suppose AC current is shooting into a wire, and the wire is attached to a bulk piece of metal off to the side of it, kind of like a ground, but not as deep as a ground. Wouldn't the bulk piece of metal work kind of like a capacitor and smooth out the voltage a bit? Everywhere I Google, I see the...
  49. genxium

    Problem on Energy Density in Dielectric Medium

    I'm reading this tutorial and having some difficulty in understanding its derivation. I take as granted that electric energy within a volume \Omega is defined by: W = \int_\Omega \phi \cdot \rho \cdot d^3r where \phi = \phi(\textbf{r}) is the eletric potential, \rho = \rho(\textbf{r}) is the...
  50. T

    Does anyone know what a Dielectric loss angle bridge is?

    All I can find on google is about what the dielectric loss angle is. I imagine the bridge is something like a Whitstone bridge but for this... Thanks
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