2014| SET 1 - (ECE GATE Exam) - Previous Question Paper Solution

Description: GATE Exam Previous Year Question Paper Solution Electronics and Communication (ECE) - 2014 (SET 1)
Number of Questions: 38
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Tags: Electronics and Communication Engineering - EC Analog Circuits Communications Differential Calculus Electronic Devices Matrices and Determinants Vector Calculus
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Choose the most appropriate phrase from the options given below to complete the following sentence.

The aircraft ________ take off as soon as its flight plan was filed.

  1. is allowed to

  2. will be allowed to

  3. was allowed to

  4. has been allowed to


Correct Option: C
Explanation:

Correct option is (3).

Read the statements: All women are entrepreneurs. Some women are doctors.

Which of the following conclusions can be logically inferred from the above statements?

  1. All women are doctors.

  2. All doctors are entrepreneurs.

  3. All entrepreneurs are women.

  4. Some entrepreneurs are doctors.


Correct Option: D
Explanation:

Correct option is (4).

For submitting tax returns, all resident males with annual income below Rs. 10 lakh should fill up Form P and all resident females with income below Rs. 8 lakh should fill up Form Q. All people with incomes above Rs. 10 lakh should fill up Form R, except non residents with income above Rs. 15 lakhs, who should fill up Form S. All others should fill Form T. An example of a person who should fill Form T is

  1. a resident male with annual income Rs. 9 lakh

  2. a resident female with annual income Rs. 9 lakh

  3. a non-resident male with annual income Rs. 16 lakh

  4. a non-resident female with annual income Rs. 16 lakh


Correct Option: B
Explanation:

Correct option is (2)

Find the odd one from the following group:

W, E, K, O I, Q, W, A F, N, T, X N, V, B, D

  1. W, E, K, O

  2. I, Q, W, A

  3. F, N, T, X

  4. N, V, B, D


Correct Option: D
Explanation:

Correct option is (4).

For matrices of same dimension M, N and scalar c, which one of these properties DOES NOT ALWAYS hold?

  1. (MT)T = M

  2. (cM)T = c(M)T

  3. (M+ N)T = MT + NT

  4. MN = NM


Correct Option: D
Explanation:

$= \begin{bmatrix} \ n_1m_1 + n_2m_3 & n_1m_2 + n_2m_4 \ \ n_3m_1 + n_4m_3 & n_3m_2 + n_4m_4 \ \end{bmatrix} \\ MN \neq NM \\ \text{i.e. property does not hold always.}$

For maximum power transfer between two cascaded sections of an electrical network, the relationship between the output impedance Z1 of the first section to the input impedance Z2 of the second section is

  1. Z2 = Z1

  2. Z2 = – Z1

  3. Z2 = Z$\begin{matrix} \ \pi \ \ 1 \ \end{matrix}$

  4. Z2 = – Z$\begin{matrix} \ \pi \ \ 1 \ \end{matrix}$


Correct Option: C
Explanation:

Choose the most appropriate word from the options given below to complete the following sentence.

Many ancient cultures attributed disease to supernatural causes. However, modern science has largely helped __________ such notions.

  1. impel

  2. dispel

  3. propel

  4. repel


Correct Option: B
Explanation:

Correct option is (2).

In the ac equivalent circuit shown in the figure, if iin is the input current and RF is very larger, the type of feedback is

  1. voltage-voltage feedback

  2. voltage-current feedback

  3. current-voltage feedback

  4. current-current feedback


Correct Option: B
Explanation:

Given the AC equivalent circuit

In the figure, assume that the forward voltage drops of the PN diode D1 and Schottky diode D2 are 0.7 V and 0.3 V, respectively. If ON denotes conducting state of the diode and OFF denotes non-conducting state of the diode, then in the circuit,

  1. both D1 and D2 are ON

  2. D1 is ON and D2 is OFF

  3. both D1 and D2 are OFF

  4. D1 is OFF and D2 is ON


Correct Option: D
Explanation:

The statistics of runs scored in a series by four batsmen are provided in the following table. Who is the most consistent batsman of these four?

   
Batsman Average Standard Deviation
K 31.2 5.21
L 46.0 6.35
M 54.4 6.22
N 17.9 5.90
  1. K

  2. L

  3. M

  4. N


Correct Option: A
Explanation:

Correct option is (1).

Consider the configuration shown in the figure which is a portion of a larger electrical network For R = 1$\Omega$ and currents i1 = 2 A, i4 = - 1A, i5 = - 4 A, which one of the following is TRUE?

  1. i6 = 5 A

  2. i3 =- 4 A

  3. Data is sufficient to conclude that the supposed currents are impossible

  4. Data is insufficient to identify the currents i2, i3, and i6


Correct Option: A
Explanation:

$= 2 - (-3) \\ = 5A$

You are given three coins: one has heads on both faces, the second has tails on both faces, and the third has a head on one face and a tail on the other. You choose a coin at random and toss it, and it comes up heads. The probability that the other face is tails is

  1. 1/4

  2. 1/3

  3. 1/2

  4. 2/3


Correct Option: B
Explanation:

Correct option is (2).

The exports and imports (in crores of Rs.) of a country from 2000 to 2007 are given in the following bar chart. If the trade deficit is defined as excess of imports over exports, in which year is the trade deficit 1/5th of the exports?

  1. 2005

  2. 2004

  3. 2007

  4. 2006


Correct Option: D
Explanation:

Correct option is (4).

If fixed positive charges are present in the gate oxide of an n-channel enhancement type MOSFET, it will lead to

  1. a decrease in the threshold voltage

  2. channel length modulation

  3. an increase in substrate leakage current

  4. an increase in accumulation capacitance


Correct Option: A
Explanation:

If fixed positive charges are present is the gate oxide of an n-channel enhancement type MOSFET, it will lead to a decrease in the threshold voltage.

A good current buffer has

  1. low input impedance and low output impedance

  2. low input impedance and high output impedance

  3. high input impedance and low output impedance

  4. high input impedance and high output impedance


Correct Option: B
Explanation:

An ideal current buffer must have the zero input impedance and infinite output impedance, i.e. Zin = 0 Zo = $\infty$ Hence, a good current buffer has low input impedance and high output impedance.

The Boolean expression $(X + Y)(X + \bar{Y}) + \overline{(X \bar{Y}) + \bar{X}}$ simplifies to

  1. X

  2. Y

  3. XY

  4. X + Y


Correct Option: C
Explanation:

C is a closed path in the z-plane by |z| = 3. The value of the integral $\oint_c \bigg(\frac{z^2 - z + 4j}{z + 2j}\bigg)dz$ is

  1. - 4$\pi$ (1 + j2)

  2. 4$\pi$ (3 - j2)

  3. - 4$\pi$ (3 + j2)

  4. 4$\pi$ (1 - j2)


Correct Option: C
Explanation:

The force on a point charge +q kept at a distance d from the surface of an infinite grounded metal plate in a medium of permittivity e is

  1. 0

  2. $\frac{q^2}{16\pi ed^2}$ away from the plate

  3. $\frac{q^2}{16\pi ed^2}$ towards the plate

  4. $\frac{q^2}{4\pi ed^2}$ towards the plate


Correct Option: C
Explanation:

A two-port network has scattering parameters given by [S] = $\begin{bmatrix} \ s_{11} & s_{12} \ \ s_{21} & s_{22} \ \end{bmatrix}$. If the port-2 of the two port is short circuited, the s11 parameter for the resultant one port network is

  1. $\frac{s_{11}-s_{11}s_{22}+S_{12}s_{21}}{1 + s_{22}}$

  2. $\frac{S_{11} + s_{11}s_{22} - s_{12}s_{21}}{1 + s_{22}}$

  3. $\frac{S_{11} + s_{11}s_{22} - s_{12}s_{21}}{1 + s_{22}}$

  4. $\frac{S_{11} - s_{11}s_{22} + s_{12}s_{21}}{1 - s_{22}}$


Correct Option: B
Explanation:

In the following circuit employing pass transistor logic, all NMOS transistors are identical with a threshold voltage of 1V. Ignoring the body-effect, the output voltages at P, Q and R are,

  1. 4 V, 3 V, 2 V

  2. 5 V, 5 V, 5 V

  3. 4 V, 4 V, 4 V

  4. 5 V, 4 V, 3 V


Correct Option: C
Explanation:

Correct option is (3).

A 230 V rms source supplies power to two loads connected in parallel. The first load draws 10 kW at 0.8 leading power factor and the second one draws 10 kVA at 0.8 lagging power factor. The complex power delivered by the source is

  1. (18 + j1.5) kVA

  2. (18 - j1.5) kVA

  3. (20 + j1.5) kVA

  4. (20 - j1.5) kVA


Correct Option: B
Explanation:

For a function g(t), it is given that $\int\limits_{-\infty}^{+ \infty}$g(t) e-jwt dt = we-2w2 for any real value w. if y(t) = $\int\limits_{-\infty}^{t}$g(T), then $\int\limits_{-\infty}^{+\infty}$y(t) dt is

  1. 0

    • j
  2. $-\frac{j}{2}$

  3. $\frac{j}{2}$


Correct Option: B
Explanation:

A discrete time signal x[n] = sin ($\pi^2$ n), n being an integer, is

  1. periodic with period $\pi$

  2. periodic with period $\pi^2$

  3. periodic with period $\frac{\pi}{2}$

  4. not periodic


Correct Option: D
Explanation:

In the circuit shown, the op-amp has finite input impedance, infinite voltage gain and zero input offset voltage. The output voltage Vout is

  1. – I2 (R1 + R2)

  2. I2 R2

  3. I1 R2

  4. – I1(R1 + R2)


Correct Option: C
Explanation:

The doping concentrations on the p-side and n-side of a silicon diode are 1 x 1016 cm-3 and 1 x 1017 cm-3, respectively. A forward bias of 0.3 V is applied to the diode. At T = 300 K, the intrinsic carrier concentration of silicon ni = 1.5 x 1010 cm-3 and $\frac{kT}{q}$ = 26 m V. The electron concentration at the edge of the depletion region on the p-side is

  1. 2.3 x 109 cm-3

  2. 1 x 1016 cm-3

  3. 1 x 1017 cm-3

  4. 2.25 x 106 cm-3


Correct Option: A
Explanation:

The digital logic shown in the figure satisfies the given state diagram when Q1 is connected to input A of the XOR gate.

Suppose the XOR gate is replaced by an XNOR gate. Which one of the following options preserves the state diagram?

  1. Input A is connected to $\overline{Q_2}$

  2. Input A is connected to $\overline{Q_2}$

  3. Input A is connected to $\overline{Q_1}$ and S is complemented

  4. Input A is connected to $\overline{Q_1}$


Correct Option: D
Explanation:

$\text{When $Q_1$, is connectede to input A, then we have the input $D_2$ as} \\ D_2 = A \oplus S \\ \hspace{0.6cm} = Q-1 \oplus S = Q_1 \bar{S} + \bar{Q_1}S$

A system is described by the following differential equation, where u(t) is the input to the system and y(t) is the output of the system. $\begin{matrix} \ . \ \ y \ \end{matrix}$ (t) + 5y(t) = u(t) when y(0) = 1 and u(t) is a unit step function, y(t) is

  1. 0.2 + 0.8e-5t

  2. 0.2 - 0.2e-5t

  3. 0.8 + 0.2e-5t

  4. 0.8 - 0.8e-5t


Correct Option: A
Explanation:

$y(t) = \frac{1}{5}u(t) + \frac{4}{5}e^{-5t} \\ \hspace{0.7cm} = 0.2 + 0.8 e^{-5t}$

Consider the Boolean function, F(w, x, y, z) = wy + xy + $\bar{w}$xyz + $\bar{w}$$\bar{x}$y + xz + $\overline{XYZ}$. Which one of the following is the complete set of essential prime implicants?

  1. w, y, xz, $\overline{XZ}$

  2. w, y, xz

  3. y, $\overline{XYZ}$

  4. y, xz, $\overline{XZ}$


Correct Option: D
Explanation:

Let x [n] = $\bigg(- \frac{1}{9} \bigg)^n$ u (n) – $\bigg(- \frac{1}{3} \bigg)^n$ u (– n – 1). The Region of Convergence (ROC) of the z-transform of x [n]

  1. is |z| > $\frac{1}{9}$

  2. is |z| < $\frac{1}{3}$

  3. is $\frac{1}{3}$ > |z| > $\frac{1}{9}$

  4. Does not exist


Correct Option: C
Explanation:

For the following feedback system G(s) = $\bigg( \frac{1}{(s + 1)(s+2)} \bigg)$. The 2% settling time of the step response is required to be less than 2 seconds.

Which one of the following compensators C(s) achieves this?

  1. 3$\bigg( \frac{1}{s + 5} \bigg)$

  2. 5$\bigg( \frac{0.03}{s} + 1\bigg)$

  3. 2(s + 4)

  4. 4$\bigg( \frac{s +8}{s + 3} \bigg)$


Correct Option: C
Explanation:

Correct option is (3).

Let X be a real-valued random variable with E[X] and E[X2] denoting the mean values of X and X2, respectively. The relation which always holds true is

  1. (E[X])2 > E[X2]

  2. (E[X])2 $\geq$ (E[X])2

  3. E[X2] = (E[X])2

  4. E[X2] > (E[X])2


Correct Option: B
Explanation:

Consider the state space model of a system, as given below:

$\begin{bmatrix} \ . \ \ x_1 \ \ . \ \ x_2 \ \ . \ \ x_3 \ \end{bmatrix}$ = $\begin{bmatrix} \ -1 & 1 & 0 \ \ 0 & -1 & 0 \ \ 0 & 0 &-2 \ \end{bmatrix}$$\begin{bmatrix} \ x_1 \ \ x_2 \ \ x_3 \ \end{bmatrix}$ + $\begin{bmatrix} \ 0 \ \ 4 \ \ 0 \ \end{bmatrix}$ u; y = $\begin{bmatrix} \ 1 & 1 & 1\ \end{bmatrix}$$\begin{bmatrix} \ x_1 \ \ x_2 \ \ x_3 \ \end{bmatrix}$

The system is

  1. controllable and observable

  2. uncontrollable and observable

  3. uncontrollable and unobservable

  4. controllable and unobservable


Correct Option: B
Explanation:

Therefore, the rank of observability matrix is Rank($O_M$) = 3 = order of system. Hence, the system is observable.

For a parallel plate transmission line, let v be the speed of propagation and Z be the characteristic impedance. Neglecting fringe effects, a reduction of the spacing between the plates by a factor of two results in

  1. halving of v and no change in Z

  2. no changes in v and halving of Z

  3. no change in both v and Z

  4. halving of both v and Z


Correct Option: B
Explanation:

Correct option is (2).

The Taylor series expansion of 3 sinx + 2 cos x is

  1. 2 + 3x – x2$\frac{x^3}{2}$ + ………

  2. 2 – 3x + x2$\frac{x^3}{2}$ + ………

  3. 2 + 3x + x2 + $\frac{x^3}{2}$ + ………

  4. 2 + 3x – x2 + $\frac{x^3}{2}$ + ………


Correct Option: A
Explanation:

The output F in the digital logic circuit shown in the figure is

  1. F = $\overline{X}$YZ + X$\overline{Y}$Z

  2. F = $\overline{X}$Y$\overline{Z}$ + X$\overline{YZ}$

  3. F = $\overline{XY}$Z + XYZ

  4. F = $\overline{XYZ}$ + XYZ


Correct Option: A
Explanation:

Consider the feedback system shown in the figure. The Nyquist plot of G(s) is also shown. Which one of the following conclusions is correct?

  1. G(s) is an all pass filter

  2. G(s) is a strictly proper transfer function

  3. G(s) is a stable and minimum phase transfer function

  4. The closed-loop system is unstable for sufficiently large and positive k


Correct Option: D
Explanation:

Consider a random process X(t) = $\sqrt{2}$ sin(2$\pi$t + $\varphi$), where the random phase $\varphi$ is uniformly distributed in the interval [0, 2$\pi$]. The auto-correlation E[X(t1) X(t2)] is

  1. cos(2$\pi$ (t1 + t2))

  2. sin(2$\pi$ (t1 – t2))

  3. sin(2$\pi$ (t1 + t2))

  4. cos(2$\pi$ (t1 – t2))


Correct Option: D
Explanation:

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