This set of Electromagnetic Theory online test focuses on “Magnetic Boundary Conditions”.
1. Find the correct relation between current density and magnetization.
a) J = Grad(M)
b) J = Div(M)
c) J = Curl(M)
d) M = Curl(J)
Explanation: The curl of the magnetization gives the magnetic field intensity theoretically. From Maxwell equation, we can correlate that with the current density (Ampere law)
2. The tangential component of the magnetic field intensity is continuous at the boundary of separation of two media. State True/False.
Explanation: For two medium of separation, the tangential component of the magnetic field intensity will be continuous. This is analogous to the fact that the tangential component of the electric field intensity is continuous at the boundary.
3. In air, the tangential component of flux density is continuous at the boundary. State True/False.
Explanation: Since the tangential component of the magnetic field intensity will be continuous and B = μH, in air, the tangential component of the flux density will also be continuous.
4. The flux density of medium 1 has a normal component of 2.4 units, then the normal component of the flux density in the medium 2 will be
Explanation: Unlike the electric fields, the magnetic flux density has normal component same in both the mediums. This gives Bn1 = Bn2.
5. The normal component of magnetic field intensity at the boundary of separation of the medium will be
Explanation: The normal component and tangential components of the magnetic flux density will be same. This holds good for any medium.
6. The line integral of the magnetic field intensity is the
a) Current density
c) Magnetic flux density
d) Magnetic moment
Explanation: The line integral of the magnetic field intensity is given by ∫H.dl. This is same as the current component. From this relation, the Ampere law can be deduced.
7. Find the magnetization of the material with susceptibility of 6 units and magnetic field intensity of 13 units.
Explanation: The magnetization is the product of the susceptibility and the magnetic field intensity. Thus M = 6 x 13 = 78 units.
8. Find the ratio of permeability of the two media when the wave is incident on the boundary at 45 degree and reflected by the boundary at 60 degree.
Explanation: From the magnetic boundary conditions, the ratio of permeability μ1/μ2 = tan θ1/tan θ2 and θ1 = 45, θ2 = 60. Thus we get μ1/μ2 = 1/√3. The ratio will be 1:√3.
9. Find the magnetic moment of a material with magnetization 5 units in a volume of 35 units.
Explanation: The magnetization is the ratio of the magnetic moment and the volume. To get moment, put M = 5 and V = 35, thus moment will be 5 x 35 = 175 units.
10. A boundary of separation between two magnetic materials is identified by which factor?
a) Change in the permeability
b) Change in permittivity
c) Change in magnetization
Explanation: Two materials are differentiated by their permeability in case of magnetic and permittivity in case of electric. Thus at the boundary of separation, change in permeability is identified for magnetic materials.
Sanfoundry Global Education & Learning Series – Electromagnetic Theory.
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