IES - Electronics Engineering - Electromagnetic Theory Qns Ly

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IES E & T Topic wise Questions Electromagnetic Theory

YEAR 1999 MCQ 1

Consider the following operations in respect of a Wheatstone bridge :(Key “Kb ”; is used for the supply battery and key “Kg ” is used for the galvanometer) 1.

Open Kb

2. Close Kg

3.

Close Kb

4. Open Kg

The correct sequence of these operations is : (A) 1, 2, 3, 4

(B) 3, 1, 2, 4

(C) 4, 3, 2, 1

(D) 3, 2, 4, 1

MCQ 2

The given fig. represents the variation of electric field 'E '

IES E & T Topic wise 1999-2009 Electromagnetic Theory

www.gatehelp.com (A) due to a spherical volume charge Q = Q1 + Q2 (B) due to two concentric shells of charges Q1 and Q2 uniformly distributed over spheres of radii R1 and R2 . (C) due to two point charge Q1 and Q2 located at any two points 'r ' ( = R1 and R2 ) (D) in a single spherical shell of charges Q uniformly distributed Q = Q1 + Q 2 MCQ 3

Two small diameter 5 g dielectric balls can slide freely on a vertical nonconducting thread. Each ball carries a negative charge of 2 μC. If the lower ball is restrained from moving, then the separation between the two balls will be (A) 8570 mm

(B) 857 mm

(C) 85.7 mm

(D) 8.57 mm

MCQ 4

Solution of Laplace’s equation, which are continuous through the second derivative, are called (A) Bessel functions

(B) odd functions

(C) harmonic functions

(D) fundamental functions

MCQ 5

Charge needed within a unit sphere centred at the origin for producing a potential field, 5 V =− 6r , for r # 1 is ε0 (A) 12πC

(B) 60πC

(C) 120πC

(D) 180πC

MCQ 6

The region between two concentric conducting cylinders with radii of 2 and 5 cm contains a volume charge distribution of − 10−8 (1 + 10r) C/cm3 . If Er and V both are zero at the inner cylinder and ε = ε0 , the potential V at the outer cylinder will be (A) 0.506 V Page 2

(B) 5.06 V

www.gatehelp.com (C) 50.6 V

IES E & T Topicwise 1999-2009 Electromagnetic Theory

(D) 506 V

MCQ 7

A 50 Ω characteristic impedance line is connected to a load which shows a reflection coefficient of 0.68. If Vin = 15 V , then the net power delivered to the load will be (A) 0.139 W

(B) 1.39 W

(C) 0.278 W

(D) 2.78 W

MCQ 8

For a transmission line with homogeneous dielectric, the capacitance per unit length is 'C ' , the relative permittivity of the dielectric is 'εr ' and velocity of light in free space is 'v ' . The characteristic impedance Z 0 is equal to (B) εr (A) εr vC vC (C)

εr vC

(D)

εr vC

MCQ 9

A dipole antenna was radiating with some excitation infree space radiating a certain amount of the power. If this antenna is immersed in a lake where water is non-magnetic and non-dissipative but has a dielectric constant of 81, the radiated power with the same excitation will (A) decrease to finite non-zero value (B) remain the same (C) increase (D) decrease to zero MCQ 10

A TEM wave impinges obliquely on a dielectric-dielectric boundary with εr1 = 2 and εr1 = 1. The angle of incidence for total reflection is : (A) 30c

(B) 60c

(C) 45c

(D) 90c Page 3


www.gatehelp.com MCQ 11

It is desired to reduce the reflected at an air porcelain by use of λ/4 plate. (For porcelain μ = μ0 and εr = 7 ). The thickness of the polystyrene plate required at 10 GHz will be (A) 5.039 cm

(B) 50.39 cm

(C) 0.5039 cm

(D) 0.05039 cm

MCQ 12

When the phase velocity of an electromagnetic wave depends on frequency in any medium, the phenomenon is called (A) scattering

(B) polarization

(C) absorption

(D) dispersion

MCQ 13

A broadside array operating at 100 cm wavelength consists of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be (A) 146 W

(B) 73 W

(C) 36.5 W

(D) 18.25 W

MCQ 14

The function F = eαz sin ω (x − vt) satisfies the wave equation v F 2 4 F = 2 provided c (A) v = c c1 + α c2 m ω

(B) v = c (1 + ω2 α2 c) −1/2

(C) v = c ω (1 + α2 c2) −1/2

2 2 −1/2 (D v = 1 c1 + ω c2 m c α

2

2

MCQ 15

An antenna has a gain of 144 dB. Assuming that the main beam of the antenna is circular in cross-section, the beam width will be

Page 4

(A) 0.4456c

(B) 1.4456c

(C) 2.4456c

(D) 3.4456c



A plane electromagnetic wave is travelling in an unbounded loss-less dielectric having μ1 = 1 and εy = 4 . The time average Poynting vector of the wave is 5 W/m3 . The phase velocity v p (assuming velocity of light as 3 # 108 m/s ) is (A) 1.5 # 108 m/s (B) 3 # 108 m/s (C) 2.5 # 105 m/s

(D) 0.5 # 108 m/s

MCQ 17

When a plane wave is incident normally from dielectric ‘1’ (μ0, ε 2 ) onto dielectric ‘2’ (μ0, ε 2 ), the electric field of the transmitted wave is − 2 times the electric field of the reflected wave. The ratio ε2 /ε1 is (A) 0.5 (B) 1 (C) 2

(D) 4

MCQ 18

If for the transmission of a parallel polarized wave from a dielectric medium of permittivity ε1 into a dielectric medium of permittivity ε 2 , there exist a value of the angle of incidence θp for which the reflection coefficient is zero, then (A) tan hθp = (C) tan θp =

ε 1 /ε 2 ε 2 /ε 1

(B) tan θp = (D) tan hθp =

ε 1 /ε 2 ε 2 /ε 1

MCQ 19

For an elliptically polarized wave incident on the interface of a dielectric at the Brewster angle, the reflected wave will be (A) elliptically polarized (B) linearly polarized (C) right circularly polarized (D) left circularly polarized MCQ 20

A rectangular waveguide 2.29 # 1.02 cm operates at a frequency of 11 GHz in TE10 mode. If the maximum potential gradient of signal is 5 kV/cm, then the maximum power handling capacity of the waveguide will be Page 5


www.gatehelp.com (A) 31.11 mW

(B) 31.11 W

(C) 31.11 kW

(D) 31.11 MW

MCQ 21

A cavity is a (A) los-pass filter

(B) high-pas filter

(C) band-pass filter

(D) band-stop filter

MCQ 22

The amounts of time-average energies stored in electric and magnetic fields for p-th mode of a cavity resonator will be (A) always equal (B) equal provide the Q-factor is very high (C) equal in the case of spherical cavities (D) equal in the case of fundamental mode of oscillation MCQ 23

A dipole antenna of λ/8 length has an equivalent total loss resistance of 1.5 Ω. The efficiency of the antenna is : (A) 0.89159 %

(B) 8.9159 %

(C) 89.159 %

(D) 891.59 %

MCQ 24

For electromagnetic wave propagation in free space, the free space is defined as (A) σ = 0, d= 1, μ = Y 1, pv ! 0, vj = 0 (B) σ = 0, d= 1, μ = 1, pv = 0, vj = 0 (C) σ = Y 0, d> 1, μ < 1, pv = Y 0, vj = 0 (D) σ = 0, d= 1, μ = 1, pv = Y 0, vj = Y 0 MCQ 25

Assertion (A) : Net charge within a conductor is always zero. Reason (R) : The conductor has a very large number of free electrons. (A) Both A and R are true and R is the correct explanation of A Page 6

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(B) Both A and R are true and R is the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 26

A quarter-wave transformer is used for matching a load of 225 ohms connected to a transmission line of 256 ohms in order to reduce the SWR along the line to 1. The characteristic impedance (in ohms) of the transformer is (A) 225

(B) 240

(C) 256

(D) 273

MCQ 27

For distortionless transmission through a channel, the channel should be such that (A) its attenuation response is an even function and phase response is an odd function of frequency (B) its attenuation response is flat and phase response is linear with frequency (C) the ratio of line inductance to line capacitance is constant (D) its termination is by a matched impedance MCQ 28

When VSWR is 3, the magnitude of the reflection coefficient will be (A) 1/4

(B) 1/3

(C) 1/2

(D) 1

MCQ 29

A coaxial RF cable has the characteristic impedance of 50 Ω and a nominal capacitance of 40 pF/m. The inductance of the cable is (A) 1 μH/m

(B) 10 μH/m

(C) 0.1 μH/m

(D) 0.0 μH/m

MCQ 30

A plane wave of 10 GHz is incident normally on a dielectric plate of Page 7


www.gatehelp.com 3 mm thickness. If the phase shift on transmission through the sheet is 90c, then the dielectric constant is (A) 2.5

(B) 3.25

(C) 4.5

(D) 6.25

YEAR 2000 MCQ 31

Match List I (Laws) with List II (Application) and select the correct answer : List-I A. Ampere’s law B.

Biot’s law

C. Coulomb’s law D. Gauss’s law List-II 1.

To find the force on a charge

2.

To find the force due to a current carrying

3.

To find the electric flux density at a point

4.

To find the magnetic flux density at a point

Codes : A

B

C

D

(A)

3

2

4

5

(B)

3

1

2

5

(C)

4

1

2

3

(D)

4

2

5

3

MCQ 32

A solid cylindrical conductor of radius ‘R’ has a uniform current density. The magnetic field ‘H’ inside the conductor at a distance ‘r’ from the axis of the conductor is (B) 1/4πr

(A) 1/2πr (C) 1r/2πR Page 8

2

(D) 1r/4πR2

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MCQ 33

The equation ΔJ = 0 is known as (A) Poisson’s equation

(B) Laplace equation

(C) Continuity equation

(D) Maxwell equation

MCQ 34

A transmission line has primary constants R, L, G and C, and secondary constants Z 0 and γ (= α + jB). If the line is lossless, then (A) R = 0, G ! 0 and α = 0 (B) R = 0, G !\ 0 and β = γ (C) G = 0 and α = β (D) R = 0, G = 0, α = 0 and β = γ MCQ 35

A transmission line having 50 Ω impedance is terminated in a load of (40 + j30) Ω . The VSWR is (A) j0.033

(B) 0.8 + j0.6

(C) 1

(D) 2

MCQ 36

A (75 − j40) Ω load is connected to a coaxial line of Z 0 = 75 Ω at 6 MHz. The load matching on the line can be MCQ 37

Polystyrene has a relative permittivity of 2.7. If the wave is incident at an angle 'θ1 ' of 30c from air onto polystyrene, the angle of transmission will be nearly (A) 0.2c

(B) 2c

(C) 18c

(D) 48c

MCQ 38

Match List-I with List-II and select the correct answer using the codes given below : (Notations have their usual meaning) : List-I

List-II Page 9


www.gatehelp.com A. Permeability

1.

QE

2.

1/ μ0 ε0

C. Velocity of CM wave

3.

μ0μr

D. Displacement density

4.

εE

B.

Force

Codes : A

B

C

D

(A)

3

2

4

5

(B)

3

1

2

5

(C)

4

1

2

3

(D)

4

2

5

3

MCQ 39

Match List-I (Antennas) with List-II (Radiation Patterns) and select the correct answer :

Codes :

(A) Page 10

A

B

C

1

2

3

www.gatehelp.com (B)

2

1

1

(C)

3

2

1

(D)

1

1

2


MCQ 40

A vertical wire of 1 mm length carries a current of 1 A at 10 MHz. The total radiated power is nearly (A) 0.13 W

(B) 0.88 W

(C) 7.3 W

(D) 73 W

MCQ 41

A Yagi antenna has a driven antenna (A) only

(B) with a reflector

(C) with one or more directors (D) with a reflector and one or more directors MCQ 42

The Poynting vector P = Ev # Hv has the dimensions of (A) Power/unit area

(B) Volts

(C) Power

(D) Volt/unit length

MCQ 43

In a hundred-turn coil, if the flux through each turn is (t3 − 2t) m Wb, the magnitude of the induced emf in the coil at a time of 4s is (A) 46 mV

(B) 56 mV

(C) 4.6 V

(D) 5.6 V

MCQ 44

Consider the following statements regarding a plane wave propagating through free space : The direction of field 1.

‘E’ is perpendicular to the direction of propagation

2.

‘H’ is perpendicular to the direction of propagation

3.

‘E’ is perpendicular to the direction of field ‘H’ Page 11


www.gatehelp.com Which of these statements are correct ? (A) 1 and 2 (B) 2 and 3 (C) 1 and 3

(D) 1, 2 and 3

MCQ 45

If the velocity of electromagnetic wave in free space is 3 # 108 m/s , the velocity in a medium with εr of 4.5 and μr of 2 would be (B) 3 # 108 m/s (A) 1 # 108 m/s (C) 9 # 108 m/s

(D) 27 # 108 m/s

MCQ 46

Phase velocity 'v p ' and the group velocity 'vg ' in a waveguide ('v' is a velocity of light) are related as (B) v p + vg = c (A) v p vg = c2 (C) v p /vg =a constant

(D) v p + vg =a constant

MCQ 47

The cut-off wavelength λc for TE20 mode for a standard rectangular waveguide is (A) 2/a (B) 2a (C) a

(D) 2a2

MCQ 48

If Hv = 0.1 sin (108 πt + βy) atx A/m for a place wave propagating in free space, then the time average Poynting vector is (B) (− 0.6πaty) W/m2 (A) (0.6π sin2 βy) aty W/m2 (D) − 1.2πatx W/m2 (C) 1.2πatx W/m2 MCQ 49

The dimension of flux density is (B) MT − 2 Q − 2 (A) MT − 1 Q − 1 (C) MT 1 Q 1

(D) MT −1 Q − 2

MCQ 50

Assertion (A) : The solution of Poission’s equation is the same as the Page 12

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solution of Laplace’s equation. Reason (R) : Laplace’s equations is a special case of Poisson’s equation for source-free regions. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true

YEAR 2001 MCQ 51

The energy stored per unit volume in an electric field (with usual notations) is given by (A) 1/2εH 2

(B) 1/2εE

(C) 1/2εE 2

(D) εE 2

MCQ 52

A positive charge of Q coulomb is located at point A (0, 0, 3) and a negative charge of magnetic Q coulombs is located at point B (0, 0, − 3) . The electric field intensity at point C (4, 0, 0) is in the (A) negative x -direction

(B) negative z -direction

(C) positive x -direction

(D) positive z -direction

MCQ 53

The force between two points charges of 1 nC each with a 1 mm separation in air is (A) 9 # 10−3 N

(B) 9 # 10−6 N

(C) 9 # 10−9 N

(D) 9 # 10−12 N

MCQ 54

A 3 μF Capacitor is charged by a constant current of 2 μA for 6 seconds. The voltage across the capacitor to the end of charging will be (A) 3 V

(B) 4 V Page 13


www.gatehelp.com (C) 6 V

(D) 9 V

MCQ 55

Consider the following statements : A parallel plane capacitor is filled with a dielectric of relativity dr1 and connected to a d.c. voltage of V volts. If the dielectric is changed to another with relative permittivity dr1= 2 dr1 , keeping the voltage constant, then 1. the electric field intensity E within the capacitor doubles. 2.

the displacement flux density D doubles

3.

the charge Q on the plates is reduced to half.

4.

the energy stored in the capacitor is doubled.

Select the correct answer using the codes given below : (A) 1 and 2 (B) 2 and 3 (C) 2 and 4

(D) 3 and 4

MCQ 56

Laplace equation in cylindrical coordinates is given by 2 2 (A) 4 2 V = 1 2 b r2V l + 12 c2 V2 m + 2 V2 = 0 r 2r 2r 2z r 2z 2 2 2 (B) 4 2 V = 2 V2 + 2 V2 + 2 V2 2x 2y 2z

(C) 4 2 V =−

ρ ε

2 (D) 4 2 V = 1 2 c r 2V m + 2 12 =0 r 2r 2r r sin θ2φ2

MCQ 57

Gauss law relates the electric field intensity E with the volume charge density ρ at a point as (B) Δ : E = ε0 ρ (A) Δ # E = ε0 ρ (C) Δ # E = ρ/ε0

(D) Δ : E = ρ/ε0

MCQ 58

The input impedance of λ/8 long short-circuited section of a lossless transmission line is Page 14


www.gatehelp.com (A) zero

(B) inductive

(C) capacitive

(D) infinite

MCQ 59

Match List I (Parameters) with List II (Values) for a transmission line with a series impedance Z = R + j ωLΩ/m and a shunt admittance Y = G + jωC mho/m , and select the correct answer : List-I

List-II

A. Characteristic impedance Z 0

1.

ZY

Propagation constant λ

2.

Z/Y

3.

Y/Z

B.

C. The sending-end input

impedance Zs when the line is terminated in its characteristic impedance Z 0 Codes : A

B

C

(A)

3

1

1

(B)

2

3

3

(C)

2

1

2

(D)

1

2

2

MCQ 60

A boundary separates two magnetic materials of permeability μ1 and μ2. The magnetic field vector in μ1 and H1 with a normal component Hn1 and tangential component Ht1 while that in μ2 is H2 with a normal component Hn 2 and a tangential component Ht 2 . Then the derived conditions would be (A) H1 = H2 and Ht 1 = Ht 2 (B) Ht 1 = Ht 2 and μ1 Hn1 = μ2 Hn 2 (C) H1 = H2 and μ1 Hn1 = μ2 Hn2 (D) H1 = H2, Ht 1 = Ht 2 and μ1 Hn 1 = μ2 Hn 2 MCQ 61

For frequencies up to 1650 kHz,t he transmitting antenna used is a Page 15


www.gatehelp.com (A) parabolic dish

(B) vertical antenna

(C) Yagi antenna

(D) turnstile antenna

MCQ 62

The radiation field of an antenna at a distance r varies as (A) 1/r

(B) 1/r 2

(C) 1/r 3

(D) 1/r 4

MCQ 63

The wave radiated by a helical antenna is (A) linearly polarized (B) right circularly polarized (C) left circularly polarized (D) elliptically polarized MCQ 64

Which one of the following is NOT a correct Maxwell equation ? (A) 4# H = 2D + J (B) 4# E = 2H 2t 2t (C) 4: D = ρ

(D) 4: B = 0

MCQ 65

In a certain microstrip path antenna, the unexcited patch is of length L, width W , thickness of the substrate being h and its relative permittivity εr . Then, the capacitance of the unexcited patch is (A) LW/εr h

(B) LW/ε0 εr h

(C) εr LW/h

(D) ε0 εr LW/h

MCQ 66

Match List I (Maxwell equation) with List II (Description) and select the correct answer :

A. Page 16

List I # Bv : dav = 0

www.gatehelp.com B.


# Dv : dav = # ρdV V

C.

# Ev : dsv =− # Bda

D.

# Hv : dsv = # (D + J) : da List II

1.

The mmf around a closed path is equal to the conduction current plus the time derivative of the electric displacement current through any surface bounded by the path.

2.

The emf around a closed path is equal to the time derivative is equal to the time derivative of the magnetic displacement through any surface bounded by the path.

3.

The total electric displacement through the surface enclosing a volume is equal to total charge within the volume

4.

The net magnetic flux emerging through any closed surface is zero.

Codes : A

B

C

D

(A)

1

3

2

4

(B)

4

3

2

1

(C)

4

2

3

1

(D)

1

2

3

4

MCQ 67

In a uniform plane wave, the value of E / H is (A)

μ/ε

(C) 1

(B)

ε/μ

(D)

με

MCQ 68

For a hollow waveguide, the axial current must necessarily be (A) a combination of conduction and displacement currents (B) time-varying conduction current and displacement current (C) time-varying conduction current and displacement current (D) displacement current only Page 17



A cylindrical cavity resonates at 9 GHz in the TE111 mode. The bandwidth 3 dB is measured to be 2.4 MHz. The Q of the cavity at 9 GHz is (A) 9000/2.4 3

(B) 9000/2.4 2

(C) 9000 # 2.4 3 / 2

(D) 9000/2.4

MCQ 70

The phenomenon of microwave signals following the curvature of earth is known as (A) Faraday effect

(B) ducting

(C) wave tilt

(D) troposcatter

MCQ 71

A radio communication link is to be established via the ionosphere. The virtual height at the mid-point of the path is 300 km and the critical frequency is 9 MHz. The maximum usable frequency for the link between the stations of distance 800 km assuming flat earth is (A) 11.25 MHz

(B) 12 MHz

(C) 15 MHz

(D) 25.5 MHz

MCQ 72

Which one of the following statements is NOT correct for a plane wave with H = 0.5e−0.1x cos (106 t − 2x) atz A/m (A) The wave frequency is 106 r.p.s (B) The wavelength is 3.14 m (C) The wave travels along + x -direction (D) The wave is polarized in the z -direction MCQ 73

A coil of resistance of 5 Ω and inductance 0.4 H is connected to a 50 V d.c. supply. The energy stored in the field is

Page 18

(A) 10 joules

(B) 20 joules

(C) 40 joules

(D) 80 joules

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MCQ 74

Assertion (A) : Programmes broadcast by radio stations operating in the medium wave band of 550 to 1650 kHz situated at long distance in excess of 500 km cannot be heard during day-time but may be heard during night time. Reason (R) : In the night-time, radio waves reflected from the F-layer suffer negligible attenuation since D-and E-layers are absent during the night-time. (A) Both A and B are true and R is the correct explanation of A (B) Both A and R are true and but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 75

Assertion (A) : For an end-fire array, the current in successive antennas must lag in phase. Reason (R) : Radiation of successive antennas will cancel along the axis. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 76

Assertion (A) : The radio horizon for space wave is more than the optical horizon. Reason (R) : The atmosphere has varying density. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true Page 19



Which of the following conditions will not guarantee a distortionless transmission line ? (A) R = G = 0 (B) RC = GL (C) Very low frequency range (R >> ωL, G >> ωC ) (D) Very high frequency range (R << ωL, G << ωC ) MCQ 78

In an air line, adjacent maxima are found at 12.5 cm and 37.5 cm. The operating frequency is (A) 1.5 GHz

(B) 600 MHz

(C) 300 MHz

(D) 1.2 GHz

MCQ 79

Fig. I shows an open circuited transmission line. The switch is closed at time t = 0 and after a time t the voltage distribution on the line reaches that shown in Fig. II. If c is the velocity in the line, then

(A) t < l/c

(B) t = l/c

(C) 1l/c > l/c

(D) t < 2l/c

YEAR 2002 MCQ 80

Assertion (A) : The greater the 'Q' , the smaller the bandwidth of a resonant circuit. Reason (R) : At high frequencies the Q of a coil falls due to skin Page 20

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effect. (A) Both A and R are true R is the correct explanation of A (B) Both A and R are true R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 81

Assertion (A) : For an E.M. wave normally incident on a conductor surface the magnetic on a conductor surface the magnetic field H undergoes a 180c phase reversal and the phase of electric field E remains same. Reason (R) : The direction of propagation of incident wave will reverse after striking a conductor surface. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 82

Assertion (A) : A λ/4 short circuited line behaves as a series resonant circuit. Reason (R) : At a particular frequency the input impedance becomes infinite. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R is true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 83

A field A = 3x 2 yza x + x 3 za y + (x 3 y − 2z) a z can be termed as (A) Harmonic (B) Divergence less (C) Solenoidal

(D) Rotational

MCQ 84 Page 21


www.gatehelp.com Consider the following : For a lossless transmission line we can write : 1.

Z in =− jZ 0 for a shorted line with 1 = λ/8

2.

Z in = ! j \ for a shorted line with = λ/4

3.

Z in = Z 0 for a matched line of any length

Select the correct answer using the codes given below : (A) 1 and 2

(B) 2 and 3

(C) 1 and 3

(D) 2 and 4

MCQ 85

The input impedance of a short circuited quarter wave long transmission lien is (A) purely reactive (B) purely resistive (C) dependent on the characteristic impedance of the line (D) none of the above MCQ 86

The current distribution along a travelling wave antenna can be written in the form (A) Z = 0 e−jβz

(B) (Z) = 0 sin βz

(C) (Z) = 0

(D) (Z) = 0 cos (ωt − βz)

MCQ 87

Match List I with List II and select the correct answer : List-I A. Propagation constant B.

Radiation intensity

C. Wave impedance List-II ωμσ/2

1.

Page 22

2

2.

r /2h ( E 2)

3.

Et /Ht

www.gatehelp.com 4.


Ev # Hv

Codes : A

B

C

(A)

1

2

3

(B)

4

3

2

(C)

1

3

2

(D)

4

2

3

MCQ 88

For a wave propagation in an air filled rectangular waveguide. (A) guided wavelength is never less than free space wavelength (B) wave impedance is never less than the free space impedance (C) TEM mode is possible if the dimensions of the waveguide are properly chosen (D) Propagation constant is always a real quantity MCQ 89

Consider the following statements with reference of Brewster angle : 1.

For oblique incidence at a boundary, there is no reflected wave is vertically polarzed.

2.

Brewstar angle can occur only at the boundary of a perfect conductor.

3.

For a horizontally polarized wave, there is no Brewster angle.

4.

When the incident wave is not fully vertically polarized, there will be a reflected component which is horizontally polarized.

Which of these statements are correct ? (A) 1, 2 and 3

(B) 2, 3 and 4

(C) 3, 4 and 1

(D) 4, 1 and 2

MCQ 90 Page 23


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The circulation of Hv around the closed contour C , shown in the fig. is : (A) 0

(B) 2l

(C) 4l

(D) 6l

MCQ 91

A transmission line of output impedance 400 Ω is to be matched to a load of 25 Ω through a quarter wavelength line. The quarter wave line characteristic impedance must be (A) 40 Ω

(B) 100 Ω

(C) 400 Ω

(D) 425 Ω

MCQ 92

If the Ev field of a plane polarized e.m. wave travelling in the Z-direction is : Ev = avx Ex + avy Ey then its Hv direction is : E E (B) avy Ex + avx y (A) avy Ex − avx y Z0 Z0 Z0 Z0 E (C) avx y − avy Ex Z0 Z0

(D) − avx

Ey v E x − ay Z0 Z0

MCQ 93

A dipole produces an electric field intensity of 1 mV/m at a distance of 2 km. The field intensity at a distance of 4 km will be (A) 1 mv/m

(B) 0.75 mv/m

(C) 0.50 mv/m

(D) 0.25 mv/m

MCQ 94

Following antenna is frequently used for local are transmission at Page 24

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UHF/VHF (A) Ground monopole

(B) Turnstile antenna

(C) Slot antenna

(D) Loop antenna

MCQ 95

Consider the following statements : For electromagnetic waves propagating in free space : 1.

electrical field is perpendicular to direction of propagation

2.

electrical field is along the direction of propagation

3.

magnetic field is perpendicular to direction of propagation

4.

magnetic field is along the direction of propagation

Which of these statements are correct ? (A) 1 and 3

(B) 1 and 4

(C) 2 and 3

(D) 2 and 4

MCQ 96

When a particular mode is excited in a wave-guide, there appears an extra electric component in the direction of propagation. The resulting mode is (A) transverse-electric (B) transverse-magnetic (C) longitudinal (D) transverse-electromagnetic MCQ 97

A lossless transmission line is connected to two identical voltage source as shown in the fig.

Page 25


www.gatehelp.com The impedance measured at the mid point AA of the line is (A) \

(B) 100

(C) 50

(D) 25

MCQ 98

The vector length of the curve μ = cos2 θ (Cylindrical Co-ordinates) from θ = 0 to θ = π is (A) 0.5

(B) 1.0

(C) 2.0

(D) π

YEAR 2003 MCQ 99

An electric charge Q is placed in a dielectric medium. Which of the following quantities are independent of the dielectric constant ε of the medium ? (A) Electric potential V and Electric field intensity E (B) Displacement density D and Displacement Ψ (C) Electric field intensity E and Displacement density D (D) Electric potential V and Displacement Ψ MCQ 100

Two coaxial cylindrical sheets of charge are present in free space, ρs = 5 C/m2 at r = 2 m and rs =− 2 C/m2 at r = 4 m . The displacement flux density D at r = 3 m is (A) D = 5a r C/m2

(B) D = 2/3a r C/m2

(C) D = 10/3a r C/m2

(D) D = 18/3a r C/m2

MCQ 101

Two thin parallel wires are carrying current along the same direction. The force experienced by one due to the other is (A) Parallel to the lines (B) Perpendicular to the lines and attractive (C) Perpendicular to the lines and repulsive (D) Zero Page 26

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MCQ 102

An electric potential field is produced in air by point charge 1 μC and 4 μC located at (− 1, 1, 5) and (1, 3, − 1) respectively. The energy stored in the field is (A) 2.57 mJ

(B) 5.14 mJ

(C) 10.28 mJ

(D) 12.50 mJ

MCQ 103

Which one of the following potentials does NOT satisfy Laplace’s Equation ? (A) V = 10xy

(B) V = R cos φ

(C) V = 10/r

(D) V = ρ cos φ + 10

MCQ 104

Laplacian of a scalar function V is (A) Gradient of V

(B) Divergence of V

(C) Gradient of the gradient of V (D) Divergence of the gradient of V MCQ 105

Match List I (Dominant Mode of Propagation) with List II (Type of transmission Structure) and select the correct answer : List-I

List-II

A. Coaxial line

1.

TE

2.

Quasi TEM

C. Microstrip line

3.

Hybrid

D. Coplanar waveguide

4.

TEM

B.

Rectangular waveguide

Codes : A

B

C

D

(A)

1

4

2

3

(B)

4

1

3

2

(C)

1

4

3

2

(D)

4

1

2

3 Page 27



In a line VSWR of a load is 6 dB. The reflection coefficient will be (A) 0.033 (B) 0.33 (C) 0.66

(D) 3.3

MCQ 107

ZL = 200 Ω and it is desired that Zi = 50 Ω . The quarterwave transformer should have a characteristic impedance of (A) 100 Ω (B) 40 Ω (C) 10,000 Ω

(D) 4 Ω

MCQ 108

A TEM wave impinges obliguely on a dielectric-dielectric boundary ( εr 1 = 2, εr 2 = 1). The angle of incidence for total reflection is (A) 30c (B) 45c (C) 60c

(D) 75c

MCQ 109

A plane electromagnetic wave travelling in a perfect dielectric medium of characteristic impedance η1 is incident normally on its impedance with another perfect dielectric medium of characteristic impedance η2 . The electric and magnetic field strengths of the incident wave are denoted by E1 and H1 respectively whereas Er and Hr denote these quantities for the reflected wave, and Et and Ht for the transmitted wave. Which of the following relations are correct ? 1. Ei = η1 Hi 2.

Er = η1 Hr

3.

Et = η2 Ht

Select the correct answer using the codes given below (A) 1, 2 and 3 (B) 1 and 2 (C) 1 and 3

(D) 2 and 3

MCQ 110

A plane electromagnetic wave travelling in a perfect dielectric medium Page 28

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of dielectric constant ε1 is incident on its boundary with another perfect dielectric medium of dielectric constant ε2 . The incident ray makes an angle of θ1 with the normal to the boundary surface. The ray transmitted into the other medium makes an angle of θ2 with the normal. If ε1 = 2ε2 and θ1 = 60c, which one of the following is correct ? (A) θ2 = 45c (B) θ2 = sin−1 0.433 (C) q2 = sin−1 0.612 (D) There will be no transmitted wave MCQ 111

In a four element Yagi-Uda antenna (A) There is one driven element, one director and two reflectors (A) There is one driven element, two directors and one reflector (C) There are two driven elements, one director and two reflectors (D) All the four elements are driven elements MCQ 112

Which one of the following Maxwell’s equations gives the basic idea of radiation ? Δ # E =− 2B/2t Δ # H = 2D/2t (B) (A) 4 4 Δ : D =− 2B/2t Δ # E = 2B/2t Δ:D = ρ Δ:B = ρ (C) (D) 3 4 Δ:D = 0 Δ # H = (2D/2t) MCQ 113

For TE or TM modes of propagation in bounded media, the phase velocity (A) is independent of frequency (B) is a linear function of frequency (C) is a non-linear function of frequency (D) Can be frequency-dependent or frequency-independent depending on the source MCQ 114 Page 29


www.gatehelp.com A waveguide operated below cut-off frequency can be used as (A) A phase shifter (B) An attenuator (C) An isolator (D) None of the above MCQ 115

Match List I (Nature of Polarization) with List II (Relationship Between X and Y Components) for a propagating wave having crosssection in the XY plane and propagating along Z -direction and select the correct answer : List-I A. Linear B.

Left circular

C. Right circular D. Elliptical List-II 1.

X and Y components are in same phase

2.

X and Y components have arbitrary phase difference

3.

X component leads Y by 90c

4. X component lags behind Y by 90c Codes : A

B

C

D

(A)

1

4

2

3

(B)

4

1

2

3

(C)

1

4

3

2

(D)

4

1

3

2

MCQ 116

An air condenser of capacitance of 0.005 μF is connected to a d.c. supply of 500 Volts, disconnected and then immersed in oil with a dielectric constant of 2.5. Energy stored in the capacitor before and after immersion, respectively is (A) 500 # 10−4 J and 250 # 10−4 J Page 30

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(B) 250 # 10−4 J and 500 # 10−4 J (C) 625 # 10−4 J and 250 # 10−4 J (D) 250 # 10−4 J and 625 # 10−4 J MCQ 117

Assertion (A) : For extremely high frequency ranges or above, compared to linear antennas, aperture antennas are more useful. Reason (R) : The larger the effective area of an antenna, the sharper is the radiated beam. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 118

Assertion (A) : The quality factor Q of a waveguide is closely related to its attenuation factor α. Reason (R) : Normally attenuation factors obtainable in waveguides are much higher than those obtainable in transmission lines. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is

YEAR 2004 MCQ 119

Which one of the following statements is correct ? A right circularly polarised wave is incident from air onto a polystyrene ( εr = 2.7 ). The reflected wave is (A) right circularly polarised (B) left circularly polarised (C) right elliptically polarised Page 31


www.gatehelp.com (D) left elliptically polarised MCQ 120

A point charge of + 10 μC placed at a distance of 5 cm from the centre of a conducting grounded sphere of radius 2 cm is shown in the diagram given below :

What is the total induced charge on the conducting sphere ? (A) 10 μC

(B) 4 μC

(C) 5 μC

(D) 12.5 μC

MCQ 121

For sea water with σ = 5 mho/m and εr = 80 , what is the distance for which radio signal can be transmitted with 90% attenuation at 25 kHz ? (A) 0.322 m

(B) 3.22 m

(C) 32.2 m

(D) 322 m

MCQ 122

Two metal rings 1 and 2 are placed in a uniform magnetic field which is decreasing with time with their planes perpendicular to the field. If the rings are identical except that ring 2 has a thin air gap in it, which one of the following statements is correct ? (A) No e.m.f is induced in ring 1 (B) An e.m.f is induced in both the rings (C) Equal Joule heating occurs in both the rings (D) Joule heating does not occur in either ring. MCQ 123

The electric field of a wave propagating through a lossless medium Page 32


www.gatehelp.com (μ0, 81ε0) is E = 10 cos (6π # 108 t − bx) a y What is the phase constant β of the wave ? (A) 2π rad/m

(B) 9π rad/m

(C) 18π rad/m

(D) 81 rad/m

MCQ 124

Which one of the following gives the values of the attenuation factor α and phase shift factor β for a wave propagated in a good dielectric having σ/ (ωε) >> 1 ? (A) α =

[ σ μ /ε ] ; β = ω με 2

(B) α =

(C) α =

[ σ μ /ε ] ;β = 2

(D) α = 0, β = ω 2 με

ωμε

μ/ε ; β = ω ωμ/ε

MCQ 125

If the phase velocity of a plane wave in a perfect dielectric is 0.4 times its value in free space, then what is the relative permittivity of the dielectric ? (A) 6.25

(B) 4.25

(C) 2.5

(D) 1.25

MCQ 126

In free space E (x, t) = 60 (ωt − 2x) a y V/m . What is the average power crossing power crossing a circular area of radius 4 m in the plane x = cons tan t ? (A) 480 W

(B) 340 W

(C) 120 W

(D) 60 W

MCQ 127

Consider the following statements regarding Smith charts : 1.

A normalized Smith chart applies to a line of any characteristic resistance and serves as well for normalized admittance

2.

A polar coordinate Smith chart contains circles of constant z and circles of constant +z

3.

In Smith chart, the distance towards the load is always measured in clockwise direction. Page 33


www.gatehelp.com Which of the statements given above are correct ? (A) 1, 2 and 3

(B) 2 and 3

(C) 1 and 3

(D) 1 and 2

MCQ 128

A ^100 − j75h Ω load is connected to a co-axial cable of characteristic impedance 75 ohms at 12 GHz. In order to obtain the best matching, which one of the following will have to be connected ? (A) A short-circuited sub at load (B) Inductance at load (C) A capacitance at a specific distance at load (D) A short-circuited stub at some specific distance from load MCQ 129

What is the effect of the earth’s magnetic field in the reflected wave at frequencies in the vicinity of gyro-frequency ? (A) No attenuation in the reflected wave (B) Decreased attenuation in the reflected wave (C) Increased attenuation in the reflected wave (D) Nominal attenuation in the reflected wave MCQ 130

Consider the following statements relating to the cavity resonators : 1.

For over-coupling the cavity terminals are at voltage maximum in the input line at resonance

2.

For over-coupling the cavity terminals are at the voltage minimum in the input line at resonance

3.

For under-coupling the normalized impedance at the voltage maximum is the standing wave ratio

4.

For over-coupling the input terminal impedance is equal to the reciprocal of the standing wave ratio

Which of the statements given above are correct ?

Page 34

(A) 1 and 2

(B) 3 and 4

(C) 1 and 3

(D) 2 and 4

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MCQ 131

Which one of the following statements is correct ? Short-circuited stubs are preferred to open-circuited stubs are preferred to opencircuited stub because the later are (A) more difficult to make and connect (B) made of a transmission line with a different characteristic impedance (C) liable to radiate energy (D) incapable of giving a full range of frequencies MCQ 132

Which one of the following statements is correct ? An antenna array consists of 5 omni-directional elements carrying equal in-phase currents. The elements are equally spaced along x -axis with the spacing between adjacent elements being equal to one wavelength. The directivity pattern will have a maximum. (A) only in x -direction (B) only in y -direction (C) both x -and y -direction (D) in the direction making an angle of 45c with x -axis. MCQ 133

Match List I (Characteristic to be Obtained) with List II (Arrangement of Radiators) and select the correct answer using the codes given below : List-I A. Concentration of radiation in azimuth B.

Concentration of radiation in elevation

C. Bi-directional pattern List-II 1.

Two radiators spaced 3λ/4 apart and fed with currents having 180c phase difference

2.

Two radiators spaced λ/4 apart and fed with currents having 180c phase difference Page 35


www.gatehelp.com 3.

Radiators arranged to form broadside array with horizontal array line

4.

Radiators arranged to form broadside array with vertical array line

Codes : A

B

C

(A)

2

4

3

(B)

3

4

2

(C)

3

1

2

(D)

2

1

3

MCQ 134

Consider the following statements relating to the microstrip lines : 1. Modes on microstrip lines are purely TEM 2.

Microstrip line is also called open strip line

3.

Radiation loss in microstrip line can be reduced by using thin high dielectric materials

4.

Conformal transformation technique is quite suitable for solving microstrip problems

Which of the following given above are correct ? (A) 1, 2 and 3 (B) 2, 3 and 4 (C) 1, 3 and 4

(D) 1, 2 and 4

MCQ 135

An infinitely long uniform charge of density 30 nC/m is located at y = 3, z = 5 . The field intensity at (0, 6, 1) is E = 64.7ay − 86.3az V/m . What is the field intensity at (5, 6, 1) ? 2 2 (A) E (B) c 2 6 +2 1 2 m E 5 +6 +1 1/2 2 2 (C) c 2 6 +2 1 2 m E 5 +6 +1

2 2 2 1/2 (D) c 5 +2 6 +2 1 m E 6 +1

MCQ 136

What is the magnetic dipole moment in Am2 for a square current loop having the vertices at the point A (10, 0, 0), B (0, 10, 0), C (− 10, 0, 0) and Page 36

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D (0, − 10, 0) and with current 0.01 A flowing in the sense ABCDA ? (B) − 2a z (A) 2a z (C) 4a z

(D) 4 (a x + a y)

MCQ 137

For an electric field E = E 0 sin ωt , what is the phase difference between the conduction current and the displacement current ? (B) 45c (A) 0c (C) 90c

(D) 180c

MCQ 138

An infinitely long line charge of uniform charge density ρ0 C/m is situated parallel to and at a distance from the grounded infinite plane conductor. This field problem can be solved by which one of the following ? (A) By conformal transformation (B) By method of images (C) By Laplace’s equation (D) By Poisson’s equation

YEAR 2005 MCQ 139

The capacitance of a parallel plate capacitor is given by ε0 εr (A/d) where A is the area of each plates. Considering fringing between the plates. Considering fringing field, under which one of the following conditions is the above expression valid ? (A) A is tending towards zero d (B) A is tending towards infinity d (C) A is 1 d (D) A is 1 εr ε0 d MCQ 140 Page 37


www.gatehelp.com Current density (vj ), in cylindrical co-ordinate system is given as : J (r, θ, z) = 0 for 0 < r < a = J 0 (r/a2) Ivz for a < r < b Where Ivz is the unit vector along z-coordinate axis. In the region, a < r < b , what is the expression for the magnitude of magnitude field intensity vector (Hv ) ? (B) J20 (r 3 + a3) (A) J20 (r 3 − a3) r r (C)

J 0 (r3 − a3) 3a2 r

(D) J 0 (r 3 − a3) 2πr

MCQ 141

The potential (scalar) distribution is given as V = 10y 4 + 20x 3 . If d0 is the permittivity of free space, what is the charge density ρ at the point (2, 0) ? (B) − 200/ε0 (A) − 200ε0 (C) 200ε0

(D) − 240ε0

MCQ 142

The x -directed electric field Ex having sinusoidal time variation e jωt and space variation in z-direction satisfies the equation 4 2 Ex = 0 under source free condition in a lossless medium. What is the solution representing propagation in positive z-direction ? (A) Ex = E 0 e−kz (B) Ex = E 0 e+jkz (C) Ex = E 0 e−jkz

(D) Ex = E 0 e+kz

MCQ 143

What is the expression for capacitance of a solid infinitely conducting solid sphere of radius 'R' in free space ? (B) 4πε0 R (A) 2πε0 R (C) 8πε0 R

(D) 0.5πε0 R

MCQ 144

Which one of the following concepts is used to find the expression of radiated Ev and Hv field due to a magnetic current element ? (A) Concept of vector magnetic potential Page 38

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(B) Concept of scalar electric potential (C) Concept of scalar magnetic potential (D) Concept of vector electric potential MCQ 145

For and electromagnetic wave incident on a conducting medium, the depth of penetration (A) Is directly proportional to the attenuation constant (B) Is inversely proportional to the attenuation constant (C) Has a logarithmic relationship with the attenuation constant (D) Is independent of the attenuation constant MCQ 146

In a transmission line the reflection coefficient at the load end is given by 0.3e−j30c. What is the reflection coefficient at a distance of 0.1 wavelength towards source ? (A) 0.3e+j30c

(B) 0.3e+j102c

(C) 0.3e+j258c

(D) 0.3e+66c

MCQ 147

To couple a coaxial line to a parallel wire, it is best to use a : (A) Balun (B) Slotted line (C) Directional coupler (D) Quarter wave transformer MCQ 148

To avoid grating lobe at any arbitrary angle of scan using a uniformly spaced array to identical radiators with inter-element spacing 'd ' and operating wavelength 'λ' , which one of the following conditions should be satisfied ? (A) d < 0.5λ

(B) d < λ

(C) 0.7λ # d < 2λ

(D) 0.5λ < d < λ

MCQ 149 Page 39


www.gatehelp.com A uniform transmission line of characteristic impedance 1000 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 : (A) 0 and 0, respectively

(B) 1 and 1, respectively

(C) 5 and 5, respectively

(D) 5 and 3, respectively

MCQ 150

A quarter wave transformer can be used for matching accurately : (A) Inductive loads only (B) Capacitive loads only (C) Loads with an nature of reactance (D) Purely resistive loads only MCQ 151

The dominant mode in a circular waveguide is a : (A) TEM mode

(B) TM 01 mode

(C) TE21 mode

(D) TE11 mode

MCQ 152

The cut-off frequency of the dominant mode of a rectangular wave guide having aspect ratio more than 2 is 10 GHz. The inner broad wall dimension is given by : (A) 3 cm

(B) 2 cm

(C) 1.5 cm

(D) 2.5 cm

MCQ 153

A uniformly spaced linear array of identical radiators having uniform amplitude of excitation and linear amplitude of excitation and linear phase variation with non zero gradient will produce : (A) Pencil beam at broadside (B) Fan beam (C) Scanned cosecant beam (D) Scanned pencil beam Page 40

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MCQ 154

For electronic scanning, the beam width with scan angle θ0 away from broadside is proportional to : (A) sec θ0

(B) cos θ0

(C) tan θ0

(D) cosec θ0

MCQ 155

In a waveguide, the evanescent modes are said to occur if : (A) The propagation constant is real (B) The propagation constant is imaginary (C) Only the TEM waves propagate (D) The signal has a constant frequency MCQ 156

A plane wave having x -directed electric field propagating in free space along the z -direction is incident on an infinite electrically conducting (perfect conductor) sheet at z = 0 plane. Which one of the following is correct ? (A) The sheet will absorb the wave (B) There will be x -directed surface electric current on the sheet (C) There will be y -directed surface electric current on the sheet (D) There will be magnetic current in the sheet. MCQ 157

Assertion (A) : A microstrip line cannot support pure TEM mode of propagation. Reason (R) : A microstrip line suffers from various forms of losses. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true

YEAR 2006 Page 41



Which one of the following is the characteristic impedance of lossless transmission line ? (A)

R/G

(B)

L/G

(C)

L/C

(D)

R/C

MCQ 159

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 B.

Reflection coefficient

C. VSWR

1.

− 1 to + 1

2.

1 to 3

3.

0 to 3

Codes : A

B

C

(A)

2

3

1

(B)

3

2

1

(C)

3

1

2

(D)

2

1

3

MCQ 160

A quarter wave impedance transformer is terminated by a short circuit. What would its input impedance be equal to ? (A) The line characteristic impedance (B) Zero (C) Infinity (D) Square root of the line characteristic impedance MCQ 161

Scattering parameters are more suited than impedance parameters to describe a waveguide junction because (A) the scattering parameters are frequency invariant whereas the impedance parameters are not so Page 42

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(B) scattering matrix is always unitary (C) impedance parameters vary over unacceptably wide ranges (D) scattering parameters are directly measurable but impedance parameters are not so MCQ 162

Match List I (Type of Antenna) with List II (Example) and select the correct answer using the code given below the lists : List-I

List-II

A. Aperture antenna

1.

Helical antenna

Circularly polarized

2.

Point source antenna

C. Frequency independent

3.

Log periodic antenna

D. Isotropic antenna

4.

Microstrip antenna

B.

Codes : A

B

C

D

(A)

3

2

4

1

(B)

4

1

3

2

(C)

3

1

4

2

(D)

4

2

3

1

MCQ 163

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. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 164

Assertion (A) : Time varying electric field produces magnetic fields. Page 43


www.gatehelp.com Reason (R) : Time varying magnetic field produces electric fields. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is NOT the correct explanation of A (C) A is true but R is false (D) A is false but R is true MCQ 165

A parallel plate capacitor has a homogeneous dielectric slab of area 4 cm2 and thickness 1 cm with εr = 4 . If a cubic air void of 1 mm3 is developed in the volume of the dielectric slab, then (A) the average voltage stress in the dielectric material will increase and discharge free rating of the capacitor will increase (B) the average voltage stress in the dielectric material will increase and discharge free rating of the capacitor will decrease (C) the average voltage stress in the dielectric material will increase and discharge free rating of the capacitor will decrease (D) the average voltage stress in the dielectric material will decrease and discharge free rating of the capacitor will increase MCQ 166

A parallel plate capacitor of 5 pF capacitor has a charge of 0.1 μC on its plates. What is the energy stored in the capacitor ? (A) 1 mJ (B) 1 μJ (C) 1 nJ

(D) 1 pJ

MCQ 167

Equivalent surface about a point charge are in which one of the following forms ? (A) Spheres (B) Planes (C) Cylinders

(D) Cubes

MCQ 168

Which one of the following is the correct expression for torque on a v is the loop moment) loop in magnetic field Bv ? (Here M v : Bv (A) Tv = 4: Bv (B) Tv = M Page 44

www.gatehelp.com v # Bv (C) Tv = M


v (D) Tv = Bv # M

MCQ 169

Match List I with List II and select the correct answer using the code given below the lists : List-I

List-II

A. Line charge

1.

Maxwell

Magnetic flux density

2.

Poynting vector

C. Displacement current

3.

Biot-Savart’s law

D. Power flow

4.

Gauss’s law

B.

Codes : A

B

C

D

(A)

1

2

4

3

(B)

4

3

1

2

(C)

1

3

4

2

(D)

4

2

1

3

MCQ 170

v represent ? What does the expression 1 Jv : A 2 (A) Electric energy density (B) Magnetic energy density (C) Power density (D) Radiation resistance MCQ 171

Consider the following statements regarding an electrostatic field : 1.

It is irrotational

2.

It is solensoidal

3.

It is static only form a macroscopic view point.

4.

Work done in moving a charge in the field form one point to another is independent of the path of movement.

Which of the statements given above are correct ? Page 45


www.gatehelp.com (A) 1, 2 and 3

(B) 1, 2 and 4

(C) Only 2 and 4

(D) 1, 3 and 4

MCQ 172

Which one of the following statements is correct ? (A) Both Laplace’s and Poission’s equations are non-linear equations (B) Laplace’s equation is non-linear but Poission’s equation is linear (C) Laplace’s equation is linear but Poission’s equation is non-linear (D) Both Laplace’s and Poisson’s equations are linear MCQ 173

A charge of 1 Coulomb is placed near a grounded conducting plate at a distance of 1 m. What is the force between them ? (B) 1 N (A) 1 N 8πε0 4πε0 (C)

1 N 16πε0

(D) 4πε0 N

MCQ 174

Which one of the following is the correct statement ? A rectangular coaxial line can support (A) only TEM mode of propagation (B) both TEM and TE modes of propagation (C) either TE or TM mode of propagation (D) TEM, TE or TM mdoe of propagation MCQ 175

Match List I (Electromagnetic Law) with List II (Different Form) and select the correct answer using the code given below the lists : List-I A. Ampere’s law

1.

Faraday’s law

2.

B. Page 46

List-II v = ρv 4: D 4: J =−2h 2t

www.gatehelp.com C. Gauss law

3.

v 4# Hv = Jv + 2D 2t

D. Current

4.

v 4# Ev =−2B 2t


Codes : A

B

C

D

(A)

1

2

3

4

(B)

3

4

1

2

(C)

1

4

3

2

(D)

3

2

1

4

MCQ 176

Which one of the following modes has the highest cut-off wavelength in a rectangular waveguide ? (A) TE10

(B) TE 01

(C) TM 01

(D) TM11

MCQ 177

The electric field component of a wave in free space is given by E = 50 sin (107 t + kz) tj V/m Which one of the following is the correct inference that can be drawn from this expression ? (A) The wave propagates along y -axis (B) The wavelength is 188.5 m (C) The wave number k = 0.33 rad/m (D) The wave attenuates as it travels MCQ 178

A uniform plane electromagnetic wave is normally incident upon thick magnetic material such that is complex permittivity is equal to its complex permeability i.e. μ * = ε *. Which one of the following is the correct statement ? Page 47


www.gatehelp.com (A) There will not be any reflection from the material (B) A part of the wave will be reflected such that reflection would be 0.5 (C) Reflection coefficient would be close to 1 (D) Transmission coefficient would be 0.9 MCQ 179

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

(B) TE 01

(C) TE11

(D) TM11

YEAR 2007 MCQ 180

Which one of the following statements is correct ? On a conducting surface boundary, electric field lines are (A) always tangential (B) always normal (C) neither tangential nor normal (D) at an angle depending on the field intensity MCQ 181

If Ev = (xt + tj ) e−jβz , then the wave is said to be which one of the following ? (A) Right circularly polarized (B) Right elliptically polarized Page 48

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(C) Left circularly polarized (D) Left elliptically polarized MCQ 182

Match List I (Frequency Range) with List II ( Wave Characteristic) and select the correct answer using the code given below the lists : List-I A. 20-100 kHz B.

100-535 kHz

C. 535-1600 kHz D. 1.6-30 MHz List-II 1.

Due to high absorption in day time, long distance communication by sky wave is not possible

2.

Day time broadcasting depends entirely on ground wave propagation

3.

Mostly ground waves up to 1000 km

4.

Mostly sky waves

Codes : A

B

C

D

(A)

3

1

2

4

(B)

3

1

4

2

(C)

1

3

2

4

(D)

1

3

4

2

MCQ 183

Which one of the following is correct ? As frequency increases, the surface resistance of a metal (A) decreases (B) increases (C) remains unchanged (D) varies in an unpredictable manner Page 49



Two conducting thin coils X and Y (identical except for a thin coil Y ) are placed in a uniform magnetic field which is decreasing at a constant rate. If the plane of the coils is perpendicular to the field lines, which of the following statement is correct ? As a result, emf is induced in (A) both the coils (B) coil Y only (C) coil X only (D) none of the two coils MCQ 185

Magnetic current is composed of which of the following ? (A) Only conduction component (B) Only displacement component (C) Both conduction and displacement components (D) Neither conduction component nor displacement component MCQ 186

Application of the method of images to a boundary value problem in electrostatics involves which one of the following ? (A) Introduction of an additional distribution of changes and removal of a set of conducting surfaces (B) Introduction of an additional distribution of charge and an additional set of conducting surfaces (C) Removal of a charge distribution and introduction of an additional set of conducting surfaces (D) Removal of a charge distribution as well as a set of conducting surfaces MCQ 187

What is the value of the magnetic vector potential due to an infinitesimally small current element, evaluated at infinite distance from it ? (A) Infinity (B) Unity Page 50

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(C) Zero (D) Any number between zero and infinity depending on the strength of the current element MCQ 188

The potential distribution V between two infinite flat metal sheets meeting at an angle θ is to be found. The left edges of the sheets are separated by an infinitesimal gap. The lower sheet is at zero potential and the upper sheet is at potential V1 . If α be the angle form V = 0 plate, what is the potential distribution ?

(A) V = V1 sin a πα k 2θ

(B) V = V1 sin a α k 2θ

(C) V = V1 sin b 3πα l 2θ

(D) V = V1 sin a α k θ

MCQ 189

W1 is the electrostatic energy stored in a system of three equal point charges arranged in a line with 0.5 m separation between them. If W2 is the energy stored with 1 m separation between them, then which one of the following is correct ? (A) W1 = 0.5W2 (B) W1 = W2 (C) W1 = 2W2

(D) W1 = 4W2

MCQ 190

What is the magnetic field intensity vector Hv between two parallel sheets with separation 'd ' along z-axis both sheets carrying surface current k = ky a y ? (A) − ky a y (B) + ky a y (C) − ky a x

(D) Zero

MCQ 191 Page 51


www.gatehelp.com The electric field intensity Ev at a point P is given by 10it + 10tj + 10kt where it, tj and kt are unit vectors in x, y and z directions respectively. If α, β, γ respectively the angles the Ev vector makes with x, y and z axes respectively, they are given by which of the following ? (A) α = β = γ = 30c (B) α = β = γ = 60c (C) α = β = γ cos−1 1 3 (D) α = β = γ = cos−1 1 3 MCQ 192

Which one of the following statements for a short circuited loss free line is not correct ? (A) The line appears are a pure reactance when viewed from the sending end (B) It can be either inductive or capacitive (C) There are no reflections in the line (D) Standing waves of voltage and current are set up along length of the lines MCQ 193

Match List I (Load impedance) with List II (Value of Reflection Coefficient) and select the correct answer using the code given below the lists : List-I A. Short Circuit B.

Open Circuit

C. Line characteristics impedance D. 2 # line characteristic impedance List-II

Page 52

1.

0

2.

−1

3.

+1

4.

+1/3

www.gatehelp.com


Codes : A

B

C

D

(A)

2

1

3

4

(B)

4

3

1

2

(C)

2

3

1

4

(D)

4

1

3

2

MCQ 194

When the reflection coefficient equals 1+0c what is the VSWR? (A) Zero (B) 1 (C) 3

(D) Infinite

MCQ 195

Match List I (Transmission Line) with List II (Characteristic Impedance) and select the correct answer using the code given below the lists : A. Coaxial line

B. Two wire line

C. Parallel plate line

D. Collinear plate

1.

R0 =

ηb , a >> b a

2. R 0

3.

R0 =

η ln (b/a) 2π

4. R 0 =

η ln 4b , b >> a π ba l η ln 2b , b >> a π ba l

Codes : Page 53


www.gatehelp.com A

B

C

D

(A)

3

4

1

2

(B)

2

1

4

3

(C)

3

1

4

2

(D)

2

4

1

3

MCQ 196

A broadside array of four isotropic point sources of same amplitude and phase, placed along x axis with a spacing of λ/2 between adjacent elements has a polar pattern consisting of which of the following ? (A) One major lobe in the +ve y -direction and one major lobe in the negative y direction and no side lobes (B) One major lobe in the +ve y -direction, one major lobe in the negative y -direction, one minor lobe in the +ve x -direction and one minor lobe in the −ve direction (C) One major lobe in the +ve y -direction one major lobe in the negative y -direction, one minor lobe in each of the four quadrants (D) Four major lobes one each in + y; − y; + x and − x directions and no other side lobes MCQ 197

Which one of the following is correct ? Normal mode helical antenna has (A) low radiation efficiency and high directive gain (B) high radiation efficiency and low directive gain (C) low radiation efficiency and low directive gain (D) high radiation efficiency and high directive gain MCQ 198

A radio frequency signal at a frequency 1000 kHz is to be received by using reflection from ionoshpere. When is it possible ? (A) At daytime only (B) By using a launch angle > 60c to normal (C) If high power is used (D) When frequency is low for broadcast use Page 54

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MCQ 199

If the reflection coefficient is 1/5, what is the corresponding VSWR ? (A) 3/2

(B) 2/3

(C) 5/2

(D) 2/5

MCQ 200

For taking antenna far field pattern, what must be the distance R, between transmitting and receiving antennas ? 2 (A) R > 2D λ

2 2 (B) R > 4D λ 3

2 (C) R > D 2 2λ

2 (D) R > 2D2 λ

MCQ 201

A transmitting antenna has a gain of 10. It is fed with a signal power of 1 W. Assuming free-space propagation, what power would be captured by a receiving antenna of effective area 1 m2 in the bore sight direction at a distance of 1 m ? (A) 10 W

(B) 1 W

(C) 2 W

(D) 0.8 W

MCQ 202

What must be angle θ of a corner reflector, such that an incident wave is reflected in the same direction ? (A) 30c

(B) 45c

(C) 60c

(D) 90c

MCQ 203 Page 55


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The hybrid T is ideal, perfectly matched on all ports. The VSWR at the input is (A) 2.0

(B) 2.5

(C) 3.0

(D) 3.5

MCQ 204

The Fraunhofer region where the pattern measurement of transmitting antenna has to be taken is form a distance of 2D , where D is the λ maximum aperture dimension and λ is the free-space wavelength. What is the region generally known as ? (A) The near field (B) The far field (C) Quiet zone (D) Induction field MCQ 205

Poynting vector is a measure of which one of the following ? (A) Maximum power flow through a surface surrounding the source (B) Average power flow through the surface (C) Instantaneous power flow through the surface (D) Power dissipated by the surface MCQ 206

Why is delay distortion in coaxial cables caused ? (A) The dielectric constant (εr ) of the dielectric filling the coaxial cable varies with frequency (B) The amplitude of the signal on the cable varies with frequency (C) The velocity of electromagnetic waves propagating on the cable varies with frequency Page 56

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(D) Because of both factor given at (A) and (C) above

YEAR 2008

MCQ 207

The line integral of the vector potential A around the boundary of a surface S represents which one of the following? (A) Flux through the surface S (B) Flux density in the surface S (C) Magnetic field intensity (D) Current density MCQ 208

What is the electric flux density (in μC/m2) at a point (6, 4, − 5) caused by a uniform surface charge density of 60 μC/m2 at a plane x = 8? (A) − 30a x

(B) − 60a x

(C) 30a x

(D) 60a x

MCQ 209

An infinitely long straight conductor located along z-axis carries a current I in the +ve z -direction. The magnetic field at any point P in the x − y plane is in which direction? (A) In the positive z -direction (B) In the negative z -direction (C) In the direction perpendicular to the radial line OP (in x − y plane) joining the origin O to the point P (D) Along the radial line OP MCQ 210

A 5 A current enters a right circular cylinder of 5 cm radius. What is the linear surface current density at the end surface? (A) (50/π) A/m

(B) (100/π) A/m

(C) (1000/π) A/m

(D) (2000/π) A/m Page 57



Of two concentric long conducting cylinders, the inner one is kept at a constant positive potential + V0 and the outer one is grounded. What is the electric field in the space between the cylinders? (A) Uniform and directed radially outwards (B) Uniform and directed radially inwards (C) Non-uniform and directed radially outwards (D) Non-uniform and directed parallel to the axis of the cylinders MCQ 212

In a charge free space, the Poisson’s equation results in which one of the following? (A) Continuity equation

(B) Maxwell’s equation

(C) Laplace equation

(D) None of the above

MCQ 213

A lossless transmission line of characteristic impedance Z 0 and length l < λ/4 is terminated at the load end by an open circuit. What is its input impedance Zs ? (A) Zs = jZ 0 tan βl

(B) Zs = jZ 0 cot βl

(C) Zs =− jZ 0 tan βl

(D) Zs =− jZ 0 tan βl

MCQ 214

Consider the following statements associated with boundary conditions between two media: 1.

Normal component of B is continuous at the surface of discontinuity.

2.

Normal component of D may or may not be continuous.

Which of the statement(s) given above is/are correct? (A) 1 only (B) 2 only (C) Both 1 and 2

(D) Neither 1 nor 2

MCQ 215

According to Poynting theorem, the vector product Ev # Hv is a measure of which one of the following? Page 58

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(A) Stored energy density of the electric field (B) Stored energy density of the magnetic (D) Power dissipated per unit volume (E) Rate of energy flow per unit area MCQ 216

If the total input power to an antenna is Wt , the radiated power is Wr , and the radiation intensity is φ, then match List-I with List-II and select the correct answer using the code given below the lists: List-I A. Power gain B. Directive gain C. Average power radiated D. Efficiency of the antenna List-II 2. Wr /4π

1. Wr /Wt 3.

4πφ/Wt

4. 4πφ/Wr

Codes : A

B

C

D

(A)

3

4

2

1

(B)

4

3

2

1

(C)

3

4

1

2

(D)

4

3

1

2

MCQ 217

Where does the maximum radiation for an end-fire array occur? (A) Perpendicular to the line of the array only (B) Along the line of the array (C) AT 45c to the line of the array (D) Both perpendicular to and along the line of the array MCQ 218 Page 59


www.gatehelp.com As the aperture area of an antenna increases, its gain (A) increases

(B) decreases

(C) remains steady

(D) behaves unpredictably

MCQ 219

Inside a waveguide with perfectly conducting walls, any current present is in the form of (A) displacement current only (B) conduction current only (C) partially displacement current and partially conduction current (D) sometimes displacement current and sometimes conduction current MCQ 220

What is the unit of measurement of surface/sheet resistivity? (A) Ohm/metre

(B) Ohm metre

(C) Ohm/sq. meter

(D) Ohm

***********

Page 60

IES - Electronics Engineering - Electromagnetic Theory Qns Ly

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