Electromagnetic theory miscellaneous


Electromagnetic theory miscellaneous

Electromagnetic Theory

  1. Match the different ionospheric layers with their virtual heights
    A. A D layer1. 180 km
    B. E layer2. 25-400 km
    C. F1 layer3. 70 km
    D.F2 layer4. 110 km









  1. View Hint View Answer Discuss in Forum

    NA

    Correct Option: D

    NA


  1. White noise is that signal whose frequency spectrum—









  1. View Hint View Answer Discuss in Forum

    White noise is a signal whose frequency spectrum has flat spectral density.

    Correct Option: B

    White noise is a signal whose frequency spectrum has flat spectral density.



  1. The spectral density of pink noise varies as—









  1. View Hint View Answer Discuss in Forum

    The spectral density of pink noise varies as 1/f2.

    Correct Option: A

    The spectral density of pink noise varies as 1/f2.


  1. When an iron core is placed between the poles of a permanent magnet as shown in figure below, the magnetic field pattern is—









  1. View Hint View Answer Discuss in Forum

    Figure (C) is the best answer.

    Correct Option: C

    Figure (C) is the best answer.



  1. For an infinite linear current, four loops are shown in the given figure. The magnetic flux should be the maximum through the loop number—









  1. View Hint View Answer Discuss in Forum

    All the loops have equal areas. B at any distance r from the wire is k/ r. For any rectangular loop of height h (in the direction of the wire) and width w (⊥ the wire), the flux φ is

    a + w
    khdr
    = kh ln
    a + w
    ara

    where a is the distance of the near side from the wire.
    Thus,
    for 1, φ1 = k l ln
    a + 1
    a

    for 2, φ2 = k 2l ln
    a + 1/2
    a

    for 3, φ3 =
    1
    k2l ln
    a + 1/4 + 1
    2a + 1/4

    for 4, φ4 = kl ln
    a + 2 l
    a

    φ1 = kl ln 1 +
    1
    2 = 2kl ln 1 +
    1
    aa

    φ3 = kl ln 1 +
    1
    4 =
    1
    kl ln 1 +
    2 l
    a + 1/42a

    The long terms do not change by significant amount. Thus, φ2 should be of highest value.
    Hence alternative (B) is the correct choice.

    Correct Option: B

    All the loops have equal areas. B at any distance r from the wire is k/ r. For any rectangular loop of height h (in the direction of the wire) and width w (⊥ the wire), the flux φ is

    a + w
    khdr
    = kh ln
    a + w
    ara

    where a is the distance of the near side from the wire.
    Thus,
    for 1, φ1 = k l ln
    a + 1
    a

    for 2, φ2 = k 2l ln
    a + 1/2
    a

    for 3, φ3 =
    1
    k2l ln
    a + 1/4 + 1
    2a + 1/4

    for 4, φ4 = kl ln
    a + 2 l
    a

    φ1 = kl ln 1 +
    1
    2 = 2kl ln 1 +
    1
    aa

    φ3 = kl ln 1 +
    1
    4 =
    1
    kl ln 1 +
    2 l
    a + 1/42a

    The long terms do not change by significant amount. Thus, φ2 should be of highest value.
    Hence alternative (B) is the correct choice.