Explanation:

The magnetic vector potential is a vector field that is defined as the curl of the magnetic field. It is a mathematical construct that is used to simplify the calculation of magnetic fields in certain situations. The magnetic vector potential is denoted by the symbol A and is defined by the following equation:

A = (1/μ) ∫ B.dl

where μ is the magnetic permeability of the medium, B is the magnetic field, and dl is an infinitesimal element of length.

Magnetic Field when Magnetic Vector Potential is a Unit Vector:

When the magnetic vector potential is a unit vector, it means that the magnitude of the vector potential is equal to one. This is a special case that occurs when the magnetic field is uniform and is directed along a single axis. In this case, the magnetic field is given by the following equation:

B = μA

where μ is the magnetic permeability of the medium and A is the magnetic vector potential.

In other words, when the magnetic vector potential is a unit vector, the magnetic field is directly proportional to the magnetic permeability of the medium. This is because the magnetic vector potential is defined as the curl of the magnetic field, and when the magnetic field is uniform and directed along a single axis, its curl is zero. Therefore, the magnetic vector potential reduces to a scalar value, which is equal to the magnitude of the magnetic field divided by the magnetic permeability of the medium.

Conclusion:

In summary, when the magnetic vector potential is a unit vector, the magnetic field is directly proportional to the magnetic permeability of the medium. This is a special case that occurs when the magnetic field is uniform and directed along a single axis. The magnetic vector potential is a mathematical construct that is used to simplify the calculation of magnetic fields in certain situations.