Worksheet: Capacitor Dielectrics

In this worksheet, we will practice describing the effect on a capacitor of the size of its plates, by how much they are separated, and by what medium separates them.

Q1:

Which of the following is a correct definition of the dielectric of a capacitor?

  • AThe dielectric of a capacitor is the difference between the charge densities at the plates of the capacitor.
  • BThe dielectric of a capacitor is the ratio of the area of the plates of the capacitor to the distance between the plates.
  • CThe dielectric of a capacitor is the difference between the electric potentials at the plates of the capacitor.
  • DThe dielectric of a capacitor is the medium contained between the plates of the capacitor.
  • EThe dielectric of a capacitor is the difference between the magnitudes of the electric fields between the plates of the capacitor.

Q2:

Which of the following correctly describes the necessary electrical properties of the dielectric of a capacitor?

  • AThe dielectric of a capacitor must be ferromagnetic.
  • BThe dielectric of a capacitor must be an electrical conductor.
  • CThe dielectric of a capacitor must be an electrical insulator.
  • DThe dielectric of a capacitor must be a semiconductor.
  • EThe dielectric of a capacitor must be a superconductor.

Q3:

Which of the following correctly describes the effect of adding a dielectric to a capacitor on the electric field between the capacitor plates? Assume that the capacitor plates are initially separated only by a vacuum.

  • AThe magnitude of the electric field decreases.
  • BThe magnitude of the electric field increases.
  • CThe electric field is converted to a magnetic field.
  • DThe electric field is unaffected.
  • EThe direction of the electric field reverses.

Q4:

The diagram shows the orientations of polarized molecules in the dielectric between the plates of a capacitor. Which of the following most correctly describes the charge on the capacitor plates? Red represents positive charge and blue represents negative charge.

  • ABoth plates are equally positively charged.
  • BThe left-hand plate is positively charged, and the right-hand plate is negatively charged.
  • CThe right-hand plate is positively charged, and the left-hand plate is negatively charged.
  • DBoth plates are equally negatively charged.
  • EThe plates are uncharged.

Q5:

The diagram shows the orientations of polarized molecules in the dielectric between the plates of a capacitor. Which of the following most correctly describes the charge on the capacitor plates? Red represents positive charge and blue represents negative charge.

  • AThe plates are uncharged.
  • BThe left-hand plate is positively charged, and the left-hand plate is uncharged.
  • CThe right-hand plate is positively charged, and the left-hand plate is negatively charged.
  • DThe right-hand plate is positively charged, and the left-hand plate is uncharged.
  • EThe left-hand plate is positively charged, and the right-hand plate is negatively charged.

Q6:

Which of the following formulas correctly relates area 𝐴 of the plates of a parallel plate capacitor to the capacitance 𝐶 of the capacitor, the permittivity 𝜀 of the medium between the plates, and the distance 𝑑 between the plates?

  • A 𝐶 = 𝜀 𝐴 𝑑
  • B 𝐶 = 𝜀 𝐴 𝑑
  • C 𝐶 = 𝜀 𝐴 𝑑
  • D 𝐶 = 𝐴 𝑑 𝜀
  • E 𝐶 = 𝜀 𝑑 𝐴

Q7:

The relative permittivity of vacuum is a dimensionless constant that is equal to one. If the space between the plates of a capacitor initially contains only a vacuum and is filled with some dielectric substance, which of the following must be true of the relative permittivity of the dielectric?

  • AThe relative permittivity is less than one.
  • BThe relative permittivity is infinite.
  • CThe relative permittivity is greater than one.
  • DThe relative permittivity is equal to one.
  • EThe relative permittivity is equal to zero.

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