What happens when a dielectric material is placed between the two charged plates of the capacitor

Due to polarization of charges on either side the dielectric, it produces an electric field of its own which acts in a firection opposite to that of the field due to the source.

true

explanation:

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.