For F1 layer the maximum ionic density is 2.3 x 104 electrons per cc. The critic

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Question
For F₁ layer the maximum ionic density is 2.3 x 10⁴ electrons per cc. The critical frequency for this layer will be
Options
A. 1.36 MHz
B. 13.6 MHz
C. 136 MHz
D. 1360 MHz

Correct Answer

13.6 MHz

Explanation

f_c = 9N_max .

Electromagnetic Field Theory problems

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1. Z_L = 200 ? and it is desired that Z_i = 50 ? The quarter wave transformer should have a characteristic impedance of
Options
A. 100 ?
B. 40 ?
C. 10000 ?
D. 4 ?

2. The input impedance of short-circuited line of length l where ?/4 < l < ?/2, is
Options
A. resistive
B. inductive
C. capacitive
D. none of the above

3. Characteristic impedance of a transmission line is 50 ?. Input impedance of the open circuited line.
Z_oc = 100 + J150 ?. When transmission line is short circuited, then value of the input impedance will be
Options
A. 50 ?
B. 100 + J150 ?
C. 7.69 + J11.54?
D. 7.69 - J11.54 ?

4. Calculate the wave impedance for TM mode in rectangular waveguide for dominant mode at 3 GHz having
Options
A. (120p) ?
B. 377 ?
C. 226 ?
D. 629 ?

5. The torque (in mm) acting on a circular current loop of radius 1 mm in the xy plane, connected at the origin and with current 0.1 A, flowing in the sense of increasing in a magnetic field
is
Options
A.
B.
C. 10^-12p
D. - 10^-12p

6. A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls calculate the phase velocity for dominant mode.
Options
A. 3 x 10⁸ m/sec
B. 5 x 10⁸ m/sec
C. 1.5 x 10⁸ m/sec
D. 9 x 10⁸ m/sec

7. A plane wave is characterized by the wave is
Options
A. linearly polarized
B. circularly polarized
C. elliptically polarized
D. unpolarized

8. Consider a 300 ?, quarter wave long at 1 GHz transmission line as shown in figure. It is connected to a 10 V, 50 ? source at one end is left open circuited at the other end. The magnitude of the voltage at the open circuit end of the line is
Options
A. 10 V
B. 5 V
C. 60 V
D. 60/7 volt

10. The displacement flux density at a point on the surface of a perfect conductor is = 2(a_x - 3 a_z)c/m² pointing away from the surface. The charge density at that point c/m² will be
Options
A. 2
B. - 2
C. 4
D. - 4

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