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ESE EC : Electromagnetics - National Champion Test

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Question 1

A broadside array of four isotropic point sources of same amplitude and phase, places along x-axis with a spacing of between adjacent elements has a polar pattern consisting of which of the following?

Question 2

Assertion (A): As the length of the resonant antenna is increased, the number of lobes increases and the direction of the major lobes is closer and closer to the direction of the dipole.
Reason (R): As the length increases, the current distribution along the wire becomes more and more uniform.

Question 3

If a dipole antenna has a radiation resistance of 73 Ω, the loss resistance of 7 Ω and the power gain is 16 dB, then the directivity is

Question 4

If the diameter of a dipole antenna is increased from then its

Question 5

Assertion (A): A microstrip line cannot support pure TEM mode of propagation.
Reason (R): A microstrip line suffers from various forms of losses.

Question 6

How many electrons will have a charge of one coulomb?
6.2 * 1018

Question 7

Current density (), in cylindrical co-ordinate system is given as
(r, , z)= 0 for 0 < r < a
= J0(r/a2) for a < r < b
Where is the unit vector along z-coordinate axis. In the region , a < r < b, what is the expression for the magnitude of magnetic field intensity vector ?

Question 8

Assertion (A): Potential everywhere on a conducting surface of infinite extent is zero,
Reason (R): Displacement density on a conducting surface is normal to the surface.

Question 9

A charge of 1 coulomb is placed near a grounded conducting plate at a distance of 1 m.
What is the force between them?

Question 10

Match List-i (Quantity) with List-ii (Range of Values) and select the correct answer using the code given below the Lists:

List-i List-ii

A. Input impedance 1. – 1 to + 1

B. Reflection coefficient 2. 1 to ∞

C. VSWR 3. 0 to ∞

Codes:
A B C

Question 11

A uniform transmission line of characteristic impedance 100 Ω and feeding a purely resistive load of 500 Ω uses single stub matching. The stub is placed at a distance d from the load. The VSWR on the length d and on the stub itself will be

Question 12

Consider the following statements:
For a 10 m long common power line connecting a switch to a light bulb
1. It is a distributed circuit.
2. Time delay for propagation through it is negligible.
3. It is in the form of a shielded coaxial cable of circular cross-section.
4. As the intensity of the lamp varies, input impedance of this line also changes.
Which of the above statements is/are correct?

Question 13

When waves travel along a transmission line from a generator to a load, through which region is power transmission taking place?

Question 14

A 75 Ω transmission line is first short-terminated and the minima locations are noted. When the short is replaced by a resistive load RL, the minima locations are not altered and the VSWR is measured to be 3. The value of RL is

Question 15

The electric field component of a wave space is given by

Which one of the following is the correct inference that can be drawn from this expression?

Question 16

What is the unit of measurement of surface/sheet resisitivity?

Question 17

An axial magnetic field a applied to a cylindrical rod. The Farady rotation of a plane polarized beam after mergence from the rod is 50. If both the field and length of the rod are doubled then the angle of rotation is

Question 18

Consider the following statements:
1. (Electric or magnetic) field must have two orthogonal linear components.
2. The two components must have the same magnitude
3. The two components must have a time-phase different of odd multiples of 900
Which of these are the necessary and sufficient conditions for a time-harmonic wave to be circularly polarized at a given point in space?

Question 19

Assuming that each loop is stationary and time varying magnetic field , induces current I, which of the configurations in the figure are correct ?
1.

2.

3.

4.

Question 20

An air-filled rectangular waveguide has dimensions of a = 6 cm and b = 4 cm. The signal frequency is 3 GHz. Match List-i with List-ii and select the correct answer using the code given below the Lists:

List-i List-ii
A. 1. 2.5 GHz
B. 2. 3.75 GHz
C. 3. 4.506 GHz
D. 4. 4.506 GHz
Codes:
A B C D

Question 21

The phase velocity of waves propagating in a hollow metal waveguide is

Question 22

A rectangular waveguide (A) is gradually deformed first into a circular waveguide (B) and back again into a rectangular waveguide (C) which is oriented through 90 ° with respect to (A). If the input mode is TE10, which mode is excited in the output waveguide (C)?

Question 23

In a waveguide, the evanescent modes are said to occur if

Question 24

Tho potential ( scalar ) distribution is given as V=10y4 + 20x3 . If is the permittivity of free space what is the charge density at the point (2, 0) ?

Question 25

Two conducting thin coils X and Y (identical except for a thin cut in coil Y) are placed in a uniform magnetic field which is decreasing at a constant rate. If the plane of the coil is perpendicular to the field lines, which of the following statements is correct ? as a result emf is induced in

Question 26

Assertion (A): In solving boundary value problems, the method of images is used .
Reason (R): By this technique conducting surface can be removed from the solution domain.

Question 27

Assertion (A) : The expression , where E is the electric field and V, is the potential is not valid for time varying fields.
Reason (R) : The curl of a gradient is identically zero.

Question 28

A 5 A current enters a right circular cylinder of 5cm radius. What is the linear surface current density at the end surface?

Question 29

Given that the electric flux density

The charge density at point (1.) is

Question 30

The mode with lowest cut-off frequency for an electromagnetic wave propagating between two perfectly conducting parallel plates of infinite extent is
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May 26ESE & GATE EC