# Electromagnetic and Transmission Lines 6

Electronic Engineering MCQ Question Papers: ENTC, IT Interview Placement

Subject:  Electromagnetic and Transmission Lines 6

Part 6: List for questions and answers of Electro Magnetics & Transmission Line

Q1. A material has conductivity of 10-2 mho/m and a relative permittivity of 4. The frequency at which conduction current in the medium is equal to displacement current is

a) 45 MHz

b) 90 MHz

c) 450 MHz

d) 900 MHz

Q2. A transmission line is feeding 1 watt of power to a horn antenna having a gain of 10 dB. The antenna is matched to the transmission line. The total power radiated by the horn antenna into the free space is

a) 10 watt

b) 1 watt

c) 0.1 watt

d) 0.01 watt

Q3. An end fire array consisting of several half-wave lengths of directive gain 40, then find the width of major lobe

a) 60

b) 50

c) 51.25

d) None of the above

Q4. A uniform plane EM wave incident normally on a plane surface of a dielectric material is reflected with a VSWR of 3. What percentage of incident power that is reflected?

a) 10%

b) 25%

c) 50%

d) 75%

Q5. Poynting vector is associated with which of the following?

a) Power flow in electromagnetic

b) Flux in magnetic field

c) Charge in electrostatic field

d) Current in electrostatic field

Q6. A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing 10 cm. And if each array element feeding with 1 amp. current and operating at same frequency then find the radiated power

a) 730 W

b) 73 W

c) 100 W

d) None

Q7. If wave of critical frequency 30 MHz is departing at an angle of 60° , then the MUF is given to be

a) 10 MHz

b) 15 MHz

c) 30 MHz

d) 60 MHz

Q8. An antenna having an effective temperature of 27°K is fed into a microwave amplifier that has an effective noise temperature of 30 K. Calculate the available noise power per unit bandwidth

a) 30 K

b) 57 K

c) 27 K

d) 3K, K is Boltzmann constant

Q9. A 10 GHz signal propagates in a waveguide with a phase velocity of 4 x 10^8 m/s. If the signal produces standing wave in the guide, then the distance between successive minimal will be

a) 10 mm

b) 20 mm

c) 30 mm

d) 40 mm

Q10. A transmission line has characteristics impedance of (75 + j 0.01) ohm and is terminated in a load impedance of (70 + j 50) ohm. The transmission coefficient will be

a) 1.70 – j 2.97

b) 0.08 + j 0.32

c) 1.32 + j 1.38

d) 1.08 + j 0.32

Q11. Maximum effective aperture of an antenna which is operating at a wavelength of 3 meters and has a directivity of 100

a) 71.68 m^2

b) 716 m^2

c) 7.16 m^2

d) 71.6 m^2

Q12. The distance between maxima and minima of a standing wave is

a) λ /4

b) λ /2

c) λ

d) 2 λ

Q13. A TV. transmitting aerial is fixed on top of a 150 metre tower located on a mountain 1200 m height. The range of transmitter is

a) 51 km

b) 152 km

c) 152 m

d) 51 m

Q14. A vertical wire of 1 meter 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

Q15. The length of half-wave antenna is at 30 MHz

a) 2.5 meter

b) 5 meter

c) 10 meter

d) 100 meter

Q16. For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the characteristic impedance will be

a) 14 ohm

b) 28 ohm

c) 39 ohm

d) 79 ohm

Q17. Which one of the following statement is not a correct for a plane wave with = 0.5e^-0.1x  cos (10^6t – 2x)az A/m?

a) The wave frequency is 10^-6 r.p.s.

b) The wavelength is 3.14 m

c) The wave travels + x direction

d) Wave is polarized in the z direction

Q18. The length of half-wave antenna is at 30 MHz

a) 2.5 meter

b) 5 meter

c) 10 meter

d) 100 meter

Q19. Beamwidth (between first nulls) will be for an antenna at 3 MHz with directivity of 100

a) 140°

b) 70°

c) 210°

d) 60°

Q20. Calculate the wave number in waveguide having dimensions 4 x 2 cm at 3 GHz

a) 6.28

b) 62.8

c) 8

d) 0

Part 6: List for questions and answers of Electroma gnetic  & Transmission Line