Tuesday, September 1, 2020

Chapter 3 : Electromagnetism - Page 3

Chapter 3 : Electromagnetism

21. Ponting theorem relating the electric intensity E, magnetic intensity 11 and the rate of energy flow per unit area at a point gives poynting vector P as equal to

A. E x H
B. E . H
C. ▽.ExH
D. E.▽xH

... Answer is (A)



22. Velocity of plane electromagnetic waves in vacuum equals

A. √(u。/ ε。)
B. √(u。 ε。)
C. 1/√(u。 ε。)
D. u。 ε

... Answer is (B)


23. For normal incidence, the angle of incidence is

A. 90°
B. 135°
D. 45°

... Answer is (C)



24. According to Snell's law, for electromagnetic waves

A.(Cos 𝛉ᵢ)/(Cos 𝛉ᵣ)=n₁/n₂
(Sin 𝛉ᵢ)/(Sin 𝛉ᵣ)=n₂/n₁
(Sin 𝛉ᵢ)/(Sin 𝛉ᵣ)=n₁/n₂
D. (Cos 𝛉ᵢ)/(Cos 𝛉ᵣ)=n₂/n₁

  ... Answer is (B)


25. Plasma signifies
A. solid dielectric
B. Electronic medium
C. gaseous medium
D. liquid medium
Answer is (C)


26. Polarization of an EM wave is taken as
normal to the direction of magnetic field
B. normal to the direction of the electric

direction of the magnetic field the
D. direction of the electric field

  ... Answer is (D)



27. The EM field and current are field concentrated close to the surface of the conductor. The phenomenon is called

A. EM concentration effect
B. Ohm's effect

Faraday's effect
D. Skin effect

... Answer is (D)


28.. When EM waves are propagated in a rectangular waveguide

A. they travel along all the four walls of the waveguide
B. they are reflected from the walls but do not travel along the walls.
they travel along the broader walls of the waveguide
D. they travel through the dielectric without touching the walls

... Answer is (B)


29. When EM waves are perfect conductor, there results incident wave

A. a weak reflected wave
B. a standing wave which is not progressing
C. a stronger
D. a stronger reflected wave is
  ... Answer is (B)


30. Brewster angle is the angle

given by 𝛉ᵦ = tan⁻¹ (√ε₂)/ε₁
for which there is reflection and the Incident wave is horizontally polarized
C. for which there is no reflection and the incident wave is vertically polarized

D. Either (A) or (C)

  ... Answer is (D)



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