What is the primary factor that determines how much the capacitance increases when an insulator is placed between the plates of a capacitor?

The primary factor that determines how much the capacitance increases when an insulator is placed between the plates of a capacitor is permittivity.

Capacitance is defined as the ability of a capacitor to store charge per unit voltage, and it is directly influenced by the dielectric material inserted between the conducting plates. The permittivity of a material is a measure of how much electrical field can penetrate it and is often represented as a factor that enhances the electric field within the material compared to the electric field in a vacuum.

When a dielectric material—characterized by its permittivity—is placed between the plates of a capacitor, it reduces the electric field strength for a given charge on the plates, which leads to an increase in capacitance. The higher the permittivity of the dielectric, the greater the increase in capacitance, since it allows for more charge to be stored for the same voltage applied across the plates.

In contrast, factors such as conductivity, inductance, and resistance do not directly relate to the enhancement of capacitance when introducing an insulator. Conductivity pertains to how well a material can conduct electricity; inductance relates to the ability to store energy in a magnetic field, and resistance involves the opposition to current flow. Thus