Q.1. Define Electromagnetic?
Answer: Electromagnetic is a branch of physics or electrical engineering which is used to study the electric and magnetic phenomenon. The electric and magnetic fields are closely related to each other.
Q.2. What is the difference between the scalar and vector?
Answer: A scalar is a quantity which is wholly characterized by its magnitude. The various example of scalar quantity are temperature, mass, volume, density, speed, electric charge etc. A vector is a quantity which is characterized by both magnitude and direction. The various examples of vector quantity are force, velocity, displacement, electric field intensity, magnetic field intensity, acceleration etc.
Q.3. Define scalar or dot product of vector.
Answer: The scalar or dot product of two vectors A and B is denoted as A.B and defined as the product of the magnitude of A, the magnitude of B and the cosine of the smaller angle between them.
Q.4. Define vector or cross product of vectors.
Answer: The vector or cross product of two vectors A and B is denoted as AXB and defined as the product of the magnitude of A and B and the sine of the smaller angle between A and B.
Q.5. How two vectors behave if their dot product is zero?
Answer: If dot product of the two vectors is zero, the two vectors are perpendicular to each other.
Q.6. How two vectors behave if their cross product is zero?
Answer: If cross product of the two vectors is zero, the two vectors are parallel to each other.
Q.7. State Divergence theorem.
Answer: The integral of the normal component of any vector field over a closed surface is equal to the integral of the divergence of this vector field throughout the volume enclosed by the closed surface.
Q.8. Define Curl of a vector.
Answer: Curl is simply defined as circulation per unit area where the closed path is vanishingly small. That is curl is defined at a point.
Q.9. State Stokes theorem.
Answer: It states that the circulation of a vector field A around a closed path C is equal to the surface integral of the curl of A over the open surface ‘S’ bounded by ‘C’ provided that A and curl of A are continuous on ‘S’.
Q.10. What is the use of divergence and curl operations?
Answer: Divergence and curl are the operations used to check the nature of field whether it is solenoidal or irrotational. A vector is said to be solenoidal when divergence of a vector is zero whereas a vector is said to be irrotational when curl of a vector is zero.
Q.11. State coulomb’s law.
Answer: Coulomb stated that the force between two very small charges separated in a vacuum or free space by a distance r (which is large compared to the size of the charge) is proportional to the multiplication of charges and inversely proportional to the square of the distance between them.
Q.12. What do you mean by harmonic field?
Answer: A scalar field is said to be harmonic in a given region, if its laplacian vanishes in that region.
Q.13. State Gauss’s law for electric field.
Answer: It states that the electric flux passing through any closed surface is equal to the total charge enclosed by that surface.
Q.14. In case of co-axial cable, what is the value of the electric field at the core of the cable and outside the conductor?
Answer: Both at the core of the cable and outside the conductor, the electric field is zero.
Q.15. What is an electric dipole?
Answer: An electric dipole is the arrangement of two point charges of equal magnitude and opposite sign, separated by a distance which is small compared to the distance of point ‘P’ at which we desire the electric field and potential. It is also called as doublet.
Q.16. What is drift velocity and how it relates to the electric field intensity?
Answer: In free space the electrons would accelerate and their velocity continuously increases in the material. The progress of the electron is hindered by regular collisions with the thermally excited crystalline lattice structure and a constant average velocity is soon attained. This velocity is known as drift velocity and it is directly proportional to electric field intensity in the given material.
Q.17. What do you mean by homogeneous medium?
Answer: A medium is homogeneous, if its physical characteristics (mass, density, molecular structure etc) do not vary from point to point. If the medium is not homogeneous, it is aid to be non-homogeneous or inhomogeneous or heterogeneous.
Q.18. What is isotropic material?
Answer: An isotropic material is one whose properties are independent of direction. The materials whose molecular structure is randomly oriented will be isotropic. However, crystalline media or certain plasma has directional characteristics. Such materials are said to be non-isotropic and anistropic.
Q.19. What do you mean by polarization?
Answer: Polarization is the creation of net charge in presence of electric field. Polarization ‘P’ is defined as total dipole moment per unit volume.
Q.20. What will be the work done in moving the charge around any closed loop?
Answer: The work done in moving the charge around any closed loop is zero.
Q.21. What do you mean by equipotential surfaces?
Answer: All the point in space at which the potential has the same value lie on a surface is called as equipotential surface or simply equipotential.
Q.22. How we can obtain quadrupole with the help of dipoles?
Answer: Placing two dipoles adjacent but with one inverted, we obtain a quadrupole and placing two quadrupoles side by side but with one inverted, we obtain an octopole.
Q.23. How potential and field of a quadrupole and octopole varies with respect to ‘r’?
Answer: The potential and field of a quadrupole vary as 1/r3 and 1/r4 respectively and for an octopole as 1/r4
Q.24. What are linear materials?
Answer: If the parameters of the material do not depend on the magnitude of the field quantities then the material is linear. A ferroelectric or ferromagnetic material is non linear because its electrical or magnetic properties depend on the strength of the applied field.
Q.25. What do you mean by convection current and conduction current?
Answer: Convection current-
- It does not involve conductors.
- So does not satisfy ohm’s law.
- This current flow through an insulating medium such as liquid, rarefied gas or a vacuum.
- Well known example is a vacuum tube in which electrons emitted by cathode flows to anode in a vacuum.
- It requires conductor.
- It satisfies ohm’s law.
- Current through any conductor is of this type.