# Home / ECE / Electromagnetic Field Thoery :: Section 1

### ECE :: Electromagnetic Field Thoery

1. ZL = 200 Ω and it is desired that Zi = 50 Ω The quarter wave transformer should have a characteristic impedance of

2.  A. 100 Ω B. 40 Ω C. 10000 Ω D. 4 Ω   3. 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 half power beamwidth

4.  A. 4° B. 2° C. 10° D. 15°   5. Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 1014 Hz in glass. Assume velocity of light is 3 x 108 m/sec in vacuum.

6.  A. 4 μm B. 3 μm C. 2 μm D. 1 μm   7. The function f(x - vot) represent which of the following?

8.  A. A stationary wave B. A wave motion in forward direction C. A wave motion in reverse direction D. None of the above   9. A broadside array operating at 100 cm wavelength consist 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

10.  A. 196 W B. 73 W C. 36.5 W D. 18.25 W   11. The input impedance of short-circuited line of length l where λ/4 < l < λ/2, is

12.  A. resistive B. inductive C. capacitive D. none of the above   13. A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode.

14.  A. 4 cm B. 1 cm C. 2 cm D. 8 cm   15. Find the radiation resistance of an antenna of length λ/10 meter?

16.  A. 8 Ω B. 780 Ω C. 7.8 Ω D. 78 Ω   17. Charge needed within a unit sphere centred at the origin for producing a potential field, 18.  A. 12 pc B. 60 pc C. 120 pc D. 180 pc   19. A rectangular metal waveguide filled with a dielectric of relative permittivity εr = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is

20.  A. 2.5 GHz B. 5 GHz C. 10 GHz D. 12.5 GHz   