Electromagnetic - Online Test

Q1. A magnetic field in air is measured to be What current distribution leads to this field ?
[Hint : The algebra is trivial in cylindrical coordinates.]

Answer : Option C
Explaination / Solution:



Q2. The divergence of the vector field  
Answer : Option D
Explaination / Solution:

Given, the vector field



Q3. Consider the following statements regarding the complex Poynting vector  for the power radiated by a point source in an infinite homogeneous and lossless medium. Re() denotes the real part of  denotes a spherical surface whose centre is at the point source, and denotes the unit surface normal on S. Which of the following statements is TRUE?
Answer : Option C
Explaination / Solution:

Power radiated from any source is constant.

Q4. Consider a closed surface S surrounding volume V. If  is the position vector of a point inside S, with  the unit normal on S, the value of the integral  is
Answer : Option D
Explaination / Solution:

From Divergence theorem, we have

The position vector 

Here, , thus


Q5. A current sheet   lies on the dielectric interface x = 0 between two dielectric media with εr1 = 5, μr1 = 1 in Region -1 (x < 0) and εr2 = 5,  μr2 = 2 in Region -2(x > 0) . If the magnetic field in Region-1 at x = 0- is the magnetic field in Region-2 at x = 0+ is


Answer : Option A
Explaination / Solution:

From boundary condition

Then from Boundary condition

Comparing we get A = 30 and B =- 10


Q6. The electric and magnetic fields for a TEM wave of frequency 14 GHz in a homogeneous medium of relative permittivity εr and relative permeability
   
Assuming the speed of light in free space to be 3 × 108 m/s, the intrinsic impedance of free space to be 120π, the relative permittivity εr of the medium and the electric field amplitude Ep are  
Answer : Option D
Explaination / Solution:

From the expressions of  we can write,


Q7. The current density in a medium is given by The total current and the average current density flowing through the portion of a spherical surface r = 0.8 m,  are given, respectively, by
Answer : Option A
Explaination / Solution:
No Explaination.