dielectric

Examples of dielectric in the following topics:

• Capacitors with Dielectrics

  • A dielectric partially opposes a capacitor's electric field but can increase capacitance and prevent the capacitor's plates from touching.
  • This interruption can come in the form of a vacuum (the absence of any matter) or a dielectric (an insulator).
  • When a dielectric is used, the material between the parallel plates of the capacitor will polarize.
  • Charges in the dielectric material line up to oppose the charges of each plate of the capacitor.
  • Describe the behavior of the dielectric material in a capacitor's electric field

• Dieletrics and their Breakdown

  • Dielectric breakdown is the phenomenon in which a dielectric loses its ability to insulate, and instead becomes a conductor.
  • Dielectric breakdown (illustrated in ) is the phenomenon in which a dielectric loses its ability to insulate, and instead becomes a conductor.
  • As a failure, there is a probabilistic element and thus a dielectric may experience a breakdown at any of a range of voltages.
  • Gaseous dielectrics commonly experience breakdown in nature (the phenomenon of lightning is the most common example).
  • Identify conditions that can lead to a dielectric breakdown and its effect on materials

• Parallel-Plate Capacitor

  • Capacitors can take many forms, but all involve two conductors separated by a dielectric material.
  • Such dielectrics are commonly composed of glass, air, paper, or empty space (a vacuum).
  • In practice, dielectrics do not act as perfect insulators, and permit a small amount of leakage current to pass through them.
  • Depending on the dielectric strength (Eds) and distance (d) between plates, a capacitor will "break" at a certain voltage (Vbd).
  • Charges in the dielectric material line up to oppose the charges of each plate of the capacitor.

• Polarization

  • Dielectric polarization is the phenomenon that arises when positive and negative charges in a material are separated.
  • For the purposes of this atom, we focus on its meaning in the context of what is known as dielectric polarization—the separation of charges in materials.
  • Positive charge in a dielectric will migrate towards the applied field, while negative charges will shift away.
  • Different materials will react differently to an induced field, depending on their dielectric constant.
  • The most basic view of dielectrics involves considering their charged components: protons and electrons.

• Parallel-Plate Capacitor

  • Between them can be a vacuum or a dielectric material, but not a conductor.
  • The maximum energy (U) a capacitor can store can be calculated as a function of Ud, the dielectric strength per distance, as well as capacitor's voltage (V) at its breakdown limit (the maximum voltage before the dielectric ionizes and no longer operates as an insulator):
  • The dielectric ensures that the charges are separated and do not transfer from one plate to the other.

• Cherenkov Radiation

  • In general the dielectric constant is a function of frequency and the frequency dependence does not change the result, so we also find that the radiation is only emitted at frequencies where $\beta\epsilon^{1/2}(\omega) > 1$, or to put it another way at frequencies where the charge exceeds the propagation speed of the radiation.
  • The total energy radiated diverges; this simply results from our assumption that the charge travels through the dielectric material forever and this assumption is easy to relax by replacing the infinite integral with one over a time $ 2T$ during which the particle travels through the dielectric
  • Again the radiation is sharply peaked at the Cherenkov angle as long as $\omega T \gg 1$ and we can integrate this result over all angles to yield the total energy per frequency emitted as the charge travels through the dielectric
  • where $2 c \beta T$ is the thickness of the dielectric region.

• Capacitance

  • The most common capacitor is known as a parallel-plate capacitor which involves two separate conductor plates separated from one another by a dielectric .
  • Ultimately, in such a capacitor, q depends on the surface area (A) of the conductor plates, while V depends on the distance (d) between the plates and the permittivity (εr) of the dielectric between them.
  • The dielectric prevents charge flow from one plate to the other.

• Induced Charge

  • Subjects that can react to inductors include conductors and dielectrics.

• Solvent Effects

  • Solvent polarity has been defined and measured in several different ways, one of the most common being the dielectric constant, ε.
  • High dielectric constant solvents such as water (ε=80), dimethyl sulfoxide (ε=48) & N,N-dimethylformamide (ε=39), usually have polar functional groups, and often high dipole moments.
  • The dielectric constants provide a measure of solvent polarity.

• Water Solubility

  • Water dissolves many ionic salts thanks to its high dielectric constant and ability to solvate ions.