Electronics and Communication Engineering - Exam Questions Papers

Exercise :: Exam Questions Papers - Exam Paper 12

84₁₆ - 2A₁₆ is equal to

A.	5A₁₆
B.	4A₁₆
C.	7A₁₆
D.	15A₁₆

Answer: Option A

Explanation:

(2A)₁₆ = (00101010)₂

2's complement = 11010110 = (D6)₁₆

(84)₁₆ + (D6)₁₆ ⇒ 1(5A)₁₆ carry discarded ⇒ (5A)₁₆ .

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Calculate the electrostatic force of repulsion between two mica particles at a distance of 10^-13 m from each other. Charge on a particle is 3.2 x 10^-19 C. (relative permittivity for mica is 5)

A.	1.843 x 10^-15 N
B.	9.2 x 10^-2 N
C.	14.41 x 10^-9 N
D.	none of these

Answer: Option D

Explanation:

By Coulomb's law:

Electrostatic force = =

= 18.43 x 10^{- 3} N.

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An electromechanical closed loop control system has the following characteristics equation :s³ + 6Ks² + (K + 2)s = 8
where K is the forward gain of the system. The condition for closed loop stability is

A.	K = 0.528
B.	K = 2
C.	K = 0
D.	K = -2528

Answer: Option A

Explanation:

s³ + 6ks² + (k + 2)s + 8 = 0

a₀ = 1, a₁ = 6k, a₂ = k + 2, a₃ = 8

Apply R.H. criteria.

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What is the propagation constant for air filled wave guide with dimensions a = 1.59" and b = 0.795" at 4.95 GHz. The wave impedance is

A.	400.94 Ω
B.	562.94 Ω
C.	502.80 Ω
D.	492.80 Ω

Answer: Option B

Explanation:

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An antenna array comprises of two dipoles that are separated by wavelength. The dipoles are fed by currents of the same magnitude and 90° in phase. The array factor is: