Download PTU B.Tech 2021 Jan EE 3rd Sem 76384 Electromagnetic Fields Question Paper

Roll No.

Total No. of Pages : 02

Total No. of Questions: 18

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B.Tech.(EE) (2018 Batch) (Sem.-3)

ELECTROMAGNETIC FIELDS

Subject Code : BTEE-304-18

M.Code : 76384

Time : 3 Hrs.

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Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

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SECTION-A

Write briefly :

1. Obtain the expression for Laplacian of a scalar field for cylindrical coordinate system.
2. State the significance of displacement current in the context of Maxwell's equations.
3. If a lightning stroke with current 50 kA occurs 100 m away from your house, calculate the magnetic flux density at your house due to the lightning stroke.

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4. Show that in a good conductor, skin depth is always much shorter than its wavelength.
5. Find V×(A×B)
6. Infinite line x = 3, z = 4 carries 16 nC/m and is located in free space above the conducting plane z = 0. Use method of images to obtain the induced surface charge density on the conducting plane at (5, -6, 0).
7. State Gauss's law.
8. Express Coulomb's law in vector form.

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9. Find the equivalent inductance of two coils connected in series. Assume the fluxes to be opposing each other.
10. Distinguish between transformer and motional emf.

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SECTION-B

11. If r = xax + yay + zaz is the position vector of (x, y, z), r = | r | and 'n' is an integer, evaluate-
    1. V×(rⁿr)

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    2. V² (ln r)
12. Find D at P (6, 8, -10) because of-
    1. Point charge of 50 mC at origin
    2. A uniform line charge ?_L = 30 µC/m on z-axis.
    3. A uniform surface charge density ?_s= 27.2 µC/m² on a plane x = 12.

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13. Prove that :

    (A×B). (C×D) = A.C B.C A.D B.D

14. Derive Biot Savart's law and Ampere's Circuital law from the concept of magnetic vector potential.
15. Obtain the intrinsic impedance for an EM wave propagating through perfect conductor.

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SECTION-C

16. State Divergence theorem and verify the same for the vector field A=r² ar + r sin? cos faf over the surface of a quarter of a hemisphere defined by 0 < r < 3, 0 < ? < p/2, 0 < f < p/2.
17. If A=2ax +4 ay and B=6ay-4a_z. Find the smaller angle between them using cross product. Verify it using dot product. Apply triangle law of vector addition to establish Coulomb's law of force between two-point charges.
18. If F=2?za? +3zsin faf - 4?cos fa_z verify Stoke's theorem for the open surface defined by z = 1, 0 < ? < 2, 0 < f < 45°. What is a time harmonic field? Derive Ampere's circuital law for time harmonic fields.

NOTE: Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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