Introduction:
In electromagnetic theory, there are several quantities that are used to describe the behavior of electromagnetic fields. These quantities can be categorized as either solenoidal or non-solenoidal. Solenoidal quantities are those that represent the flow or circulation of the field, while non-solenoidal quantities represent the sources or sinks of the field.

Solenoidal and Non-solenoidal Quantities:
In electromagnetism, the solenoidal quantities are associated with the concept of divergence, which describes the behavior of the field lines as they flow or circulate. On the other hand, non-solenoidal quantities are associated with the concept of curl, which describes the rotational behavior of the field lines.

Explanation:
The solenoidal quantity in electromagnetic theory is the magnetic flux density, also known as the magnetic field B. It is given by the equation B = μH, where H is the magnetic field intensity and μ is the permeability of the medium.

Electric Field Intensity (E):
The electric field intensity is a non-solenoidal quantity in electromagnetic theory. It represents the electric field created by electric charges, which act as sources or sinks of the electric field. The electric field lines originate from positive charges and terminate on negative charges.

Electric Flux Density (D):
The electric flux density is also a non-solenoidal quantity. It represents the total electric flux passing through a given area. Electric flux density is related to the electric field intensity by the equation D = εE, where ε is the permittivity of the medium.

Magnetic Field Intensity (H):
The magnetic field intensity is a solenoidal quantity. It represents the flow or circulation of the magnetic field lines. Magnetic field lines form closed loops, similar to how water flows in a closed circuit. The magnetic field intensity is related to the magnetic field density by the equation B = μH, where μ is the permeability of the medium.

Magnetic Flux Density (B):
The magnetic flux density is the solenoidal quantity in electromagnetic theory. It represents the flow or circulation of the magnetic field lines. Magnetic flux density is related to the magnetic field intensity by the equation B = μH, where μ is the permeability of the medium.

Conclusion:
In electromagnetic theory, the solenoidal quantity is the magnetic flux density (B), while the non-solenoidal quantities are the electric field intensity (E) and the electric flux density (D). The solenoidal quantities represent the flow or circulation of the field lines, while the non-solenoidal quantities represent the sources or sinks of the field.