Electromagnetic theory miscellaneous Easy Questions and Answers | Page - 50

Electromagnetic theory miscellaneous

The critical frequency of an ionosphere layer is 10 MHz. What is the maximum launching angle from the horizon for which a 20 MHz wave will be reflected by the layer—

1. 0º
1. 30º
1. 60º
1. 90º

View Hint View Answer Discuss in Forum

f_c = 10 MHz
MUF = sec θ. f_c
20 = 10 sec θ
sec θ = 2;
Therefore θ = 60º (angle of incidence)
hence, launching angle
= 180 – (90 + 60) = 30º.

Correct Option: B

f_c = 10 MHz
MUF = sec θ. f_c
20 = 10 sec θ
sec θ = 2;
Therefore θ = 60º (angle of incidence)
hence, launching angle
= 180 – (90 + 60) = 30º.

A metal sphere with 1 m radius and a surface charge density of 10 coulomb/m2 is enclosed in a cube of 10 m side. The total outward electric displacement normal to the surface of the cube is—

1. 40 coulomb
1. 10 coulomb
1. 5 coulomb
1. None of the above

View Hint View Answer Discuss in Forum

D = 4πr²q
= 4 π.1².10
= 40 π coulomb.

Correct Option: A

D = 4πr²q
= 4 π.1².10
= 40 π coulomb.

A transverse electromagnetic wave with circular polarization is received by a dipole antenna. Due to polarization mismatch, the power transfer efficiency from the wave to the antenna is reduced to about—

1. 50%
1. 33.3%
1. 25%
1. 0%

View Hint View Answer Discuss in Forum

NA

Correct Option: A

NA

The capacitance per unit length and the characteristic impedance of a lossless transmission line are C and Z0 respectively. The velocity of a travelling wave on the transmission line is—

1. Z₀ C
1. I/ (Z₀ C)
1. Z₀/ C
1. C/ Z₀

View Hint View Answer Discuss in Forum

V₀ = 1/

√LC and Z₀ √L/C

L = CZ²₀

V₀ = 1/

√C × CZ²₀ = 1/Z₀C

Correct Option: B

V₀ = 1/

√LC and Z₀ √L/C

L = CZ²₀

V₀ = 1/

√C × CZ²₀ = 1/Z₀C

Unit of displacement density is—

1. Coulomb/metre
1. Coulombs/(metre)²
1. Newton's law
1. Maxwell's equations

View Hint View Answer Discuss in Forum

Unit of displacement density is coulombs/metre².

Correct Option: B

Unit of displacement density is coulombs/metre².