Dielectrics Practice Test

A capacitor’s dielectric is an insulating material that polarizes in an electric field, reducing the internal electric field and increasing the capacitor’s ability to store charge at a given voltage. The dielectric constant $\kappa$ indicates how much larger the capacitance is compared with no dielectric. If the original capacitance is $C_0$, then with dielectric $$C=\kappa C_0.$$ In electronics, swapping from air to a ceramic dielectric can greatly increase capacitance without changing the capacitor’s size.

Based on the passage above, if the dielectric constant doubles, how is the capacitance affected?

Consider a parallel-plate capacitor connected to a battery so the voltage is fixed. A dielectric is an insulating material whose molecules polarize, creating bound charges that oppose the applied field. This polarization reduces the electric field inside the dielectric compared with the vacuum field for the same free charge. The capacitance without dielectric is $C_0$, and inserting a dielectric with constant $\kappa$ gives $$C=\kappa C_0.$$ A common example is a plastic-film capacitor, where the film acts as the dielectric to increase capacitance.

Based on the passage above, in the context of the passage, explain how dielectric materials influence the electric field between capacitor plates.