When a dielectric material is inserted into a capacitor, what is the primary effect on the electric field within the capacitor?

When a dielectric is put into a capacitor, the molecules inside the dielectric become polarized, creating an internal electric field that opposes the external field from the plates. This opposing field effectively weakens the net electric field between the plates, so the field inside the capacitor is smaller than it would be with a vacuum. Because the field is weaker, the same amount of charge on the plates produces a higher voltage, which is why the capacitance increases by the dielectric constant. For example, inserting a plastic sheet (εr ≈ 2. 5) into a 10 µF air capacitor can raise the capacitance to about 25 µF while the field inside drops roughly to one‑fourth of its original value.