Recent questions tagged tifr2013 / GO Electronics

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TIFR ECE 2013 | Question: 1
The unit step response of a discrete-time, linear, time-invariant system is \[ y[n]=\left\{\begin{array}{rl} 0, & n<0 \\ 1, & n \geq 0 \text { and } n \text { even } \\ -1, & n \geq 0 \text { and } ... the system is bounded-input, bounded-output $\text{(BIBO)}$ stable there is not enough information to determine $\text{(BIBO)}$ stability none of the above

The unit step response of a discrete-time, linear, time-invariant system is\[y[n]=\left\{\begin{array}{rl}0, & n<0 \\1, & n \geq 0 \text { and } n \text { even } \\-1, & ...

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2

TIFR ECE 2013 | Question: 2
The output $\{y(n)\}$ of a discrete time system with input $\{x(n)\}$ is given by \[ y(n)=\sum_{k=0}^{N-1} a^{k} x(n-k) . \] The difference equation for the inverse system is given by $y(n)=x(n)-a x(n-1)$ ... $(a)$ above, otherwise the inverse does not exist If $|a|<1$, then the answer is $(b)$ above, otherwise the inverse does not exist None of the above

The output $\{y(n)\}$ of a discrete time system with input $\{x(n)\}$ is given by\[y(n)=\sum_{k=0}^{N-1} a^{k} x(n-k) .\]The difference equation for the inverse system is...

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3

TIFR ECE 2013 | Question: 3
$X$ and $Y$ are jointly Gaussian random variables with zero mean. A constant-pdf contour is where the joint density function takes on the same value. If the constant-pdf contours of $X, Y$ are as shown above, which of the following could their covariance matrix $\mathbf{K}$ ... $\mathbf{K}=\left[\begin{array}{cc}1 & -0.5 \\ -0.5 & 2\end{array}\right]$

$X$ and $Y$ are jointly Gaussian random variables with zero mean.A constant-pdf contour is where the joint density function takes on the same value. If the constant-pdf c...

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4

TIFR ECE 2013 | Question: 4
Consider a fair coin that has probability $1 / 2$ of showing heads $(\text{H})$ in a toss and $1 / 2$ of showing tails $(\text{T})$. Suppose we independently flip a fair coin over and over again. What is the probability that $\text{HT}$ sequence occurs before $\text{TT}?$ $3 / 4$ $1 / 2$ $2 / 3$ $1 / 3$ $1 / 4$

Consider a fair coin that has probability $1 / 2$ of showing heads $(\text{H})$ in a toss and $1 / 2$ of showing tails $(\text{T})$. Suppose we independently flip a fair ...

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TIFR ECE 2013 | Question: 5
Let $x(n)=\sin (2 \pi k n / N), n=0,1, \ldots, N-1$, where $2 k \neq N$ and $0<k \leq N-1$. Then the circular convolution of $\{x(n)\}$ with itself is $N \cos (4 \pi k n / N)$ $N \sin (4 \pi k n / N)$ $-N \cos (2 \pi k n / N) / 2$ $-N \sin (2 \pi k n / N) / 2$ None of the above

Let $x(n)=\sin (2 \pi k n / N), n=0,1, \ldots, N-1$, where $2 k \neq N$ and $0<k \leq N-1$. Then the circular convolution of $\{x(n)\}$ with itself is$N \cos (4 \pi k n /...

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6

TIFR ECE 2013 | Question: 6
The two-dimensional Fourier transform of a function $f(t, s)$ is given by \[ F(\omega, \theta)=\int_{-\infty}^{\infty} \int_{-\infty}^{\infty} f(t, s) \exp (-j \omega t) \exp (-j \theta s) d t d s . \] Let $\delta(t)$ be the delta function and let $u(t)=0$ ... $\exp (-(t+s)) u(t+s)$ $\exp (-t) u(t) \delta(s)$ $\exp (-t) \delta(t+s)$ None of the above

The two-dimensional Fourier transform of a function $f(t, s)$ is given by\[F(\omega, \theta)=\int_{-\infty}^{\infty} \int_{-\infty}^{\infty} f(t, s) \exp (-j \omega t) \e...

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7

TIFR ECE 2013 | Question: 7
The $Z$-transform of $\{x(n)\}$ is defined as $X(z)=\sum_{n} x(n) z^{-n}$ (for those $z$ for which the series converges). Let $u(n)=1$ for $n \geq 0$ and $u(n)=0$ for $n<0$. The inverse $Z$-transform of $X(z)=$ ... is (a), otherwise the inverse is not well-defined If $|a|<1$, then the answer is (b), otherwise the inverse is not well-defined None of the above

The $Z$-transform of $\{x(n)\}$ is defined as $X(z)=\sum_{n} x(n) z^{-n}$ (for those $z$ for which the series converges). Let $u(n)=1$ for $n \geq 0$ and $u(n)=0$ for $n<...

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8

TIFR ECE 2013 | Question: 8
The following circuit with an ideal operational amplifier is A low pass filter A high pass filter A bandpass filter A bandstop filter An all pass amplifier

The following circuit with an ideal operational amplifier isA low pass filterA high pass filterA bandpass filterA bandstop filterAn all pass amplifier

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9

TIFR ECE 2013 | Question: 9
Let $X$ and $Y$ be two zero mean independent continuous random variables. Let $Z_{1}=\max (X, Y)$, and $Z_{2}=\min (X, Y)$. Then which of the following is TRUE. $Z_{1}$ and $Z_{2}$ are uncorrelated. $Z_{1}$ and $Z_{2}$ are independent. $P\left(Z_{1}=Z_{2}\right)=\frac{1}{2}$. Both $(a)$ and $(c)$ Both $(a)$ and $(b)$

Let $X$ and $Y$ be two zero mean independent continuous random variables. Let $Z_{1}=\max (X, Y)$, and $Z_{2}=\min (X, Y)$. Then which of the following is TRUE.$Z_{1}$ an...

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10

TIFR ECE 2013 | Question: 10
Consider the following series of square matrices: \[ \begin{array}{l} H_{1}=[1], \\ H_{2}=\left[\begin{array}{cc} 1 & 1 \\ 1 & -1 \end{array}\right], \end{array} \] and for $k=2,3, \ldots$, the $2^{k} \times 2^{k}$ matrix $H_{2^{k}}$ is recursively defined as \[ H_{2^{k}}=\ ... is $H_{2^{k}} H_{2^{k}}^{T}?)$ $0$ $2^{k}$ $2^{k / 2}$ $2^{k 2^{k-1}}$ $2^{k 2^{k}}$

Consider the following series of square matrices:\[\begin{array}{l}H_{1}= , \\H_{2}=\left[\begin{array}{cc}1 & 1 \\1 & -1\end{array}\right],\end{array}\]and for $k=2,3, \...

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11

TIFR ECE 2013 | Question: 11
Two matrices $A$ and $B$ are called similar if there exists another matrix $S$ such that $S^{-1} A S=B$. Consider the statements: If $A$ and $B$ are similar then they have identical rank. If $A$ and $B$ ... Both $\text{I}$ and $\text{II}$ but not $\text{III}$. All of $\text{I}, \text{II}$ and $\text{III}$.

Two matrices $A$ and $B$ are called similar if there exists another matrix $S$ such that $S^{-1} A S=B$. Consider the statements:If $A$ and $B$ are similar then they have...

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12

TIFR ECE 2013 | Question: 12
Let $A$ be a Hermitian matrix and let $I$ be the Identity matrix with same dimensions as $A$. Then for a scalar $\alpha>0, A+\alpha I$ has the same eigenvalues as of $A$ but different eigenvectors the same eigenvalues and eigenvectors as of ... those of $A$ and same eigenvectors as of $A$ eigenvalues and eigenvectors with no relation to those of $A$ None of the above

Let $A$ be a Hermitian matrix and let $I$ be the Identity matrix with same dimensions as $A$. Then for a scalar $\alpha>0, A+\alpha I$ hasthe same eigenvalues as of $A$ b...

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13

TIFR ECE 2013 | Question: 13
Let $A$ be a square matrix and $x$ be a vector whose dimensions match $A$. Let $B^{\dagger}$ be the conjugate transpose of $B$. Then which of the following is not true: $x^{\dagger} A^{2} x$ is always non-negative $x^{\dagger} A x$ ... $A=A^{\dagger}$ then $x^{\dagger} A y$ is complex for some vector $y$ with same dimensions as $x$

Let $A$ be a square matrix and $x$ be a vector whose dimensions match $A$. Let $B^{\dagger}$ be the conjugate transpose of $B$. Then which of the following is not true:$x...

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14

TIFR ECE 2013 | Question: 14
$X, Y, Z$ are integer valued random variables with the following two properties: $X$ and $Y$ are independent. For all integer $x$, conditioned on the event $\{X=x\}$, we have that $Y$ and $Z$ are independent (in other words, conditioned on ... and $Z$ are independent Conditioned on $Z$, the random variables $X$ and $Y$ are independent All of the above None of the above

$X, Y, Z$ are integer valued random variables with the following two properties:$X$ and $Y$ are independent.For all integer $x$, conditioned on the event $\{X=x\}$, we ha...

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15

TIFR ECE 2013 | Question: 15
Consider a sequence of non-negative numbers $\left\{x_{n}: n=1,2, \ldots\right\}$. Which of the following statements cannot be true? $\sum_{n=1}^{\infty} x_{n}=\infty$ but $x_{n}$ decreases to zero as $n$ increases. $\sum_{n=1}^{\infty} x_{n}<\infty$ ... and each $x_{n} \leq 1 / n^{2}$. $\sum_{n=1}^{\infty} x_{n}<\infty$ and each $x_{n}>x_{n+1}$.

Consider a sequence of non-negative numbers $\left\{x_{n}: n=1,2, \ldots\right\}$. Which of the following statements cannot be true?$\sum_{n=1}^{\infty} x_{n}=\infty$ but...

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16

TIFR ECE 2013 | Question: 16
A surprise quiz contains three multiple choice questions; question $1$ has $3$ suggested answers, question $2$ has four, and question $3$ has two. A completely unprepared student decides to choose the answers at random. If $X$ is the number of questions the student answers ... expected number of correct answers is $15 / 12$ $7 / 12$ $13 / 12$ $18 / 12$ None of the above

A surprise quiz contains three multiple choice questions; question $1$ has $3$ suggested answers, question $2$ has four, and question $3$ has two. A completely unprepared...

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17

TIFR ECE 2013 | Question: 17
Consider four coins, three of which are fair, that is they have heads on one side and tails on the other and both are equally likely to occur in a toss. The fourth coin has heads on both sides. Given that one coin amongst the four is picked at random and is tossed, and the ... is the probability that its other side is tails? $1 / 2$ $3 / 8$ $3 / 5$ $3 / 4$ $5 / 7$

Consider four coins, three of which are fair, that is they have heads on one side and tails on the other and both are equally likely to occur in a toss. The fourth coin h...

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18

TIFR ECE 2013 | Question: 18
Consider a coin tossing game between Santa and Banta. Both of them toss two coins sequentially, first Santa tosses a coin then Banta and so on. Santa tosses a fair coin: Probability of heads is $1 / 2$ and probability of tails is $1 / 2$. Banta's coin probabilities depend on ... the two trials conducted by each of them? $1 / 2$ $5 / 16$ $3 / 16$ $1 / 4$ $1 / 3$

Consider a coin tossing game between Santa and Banta. Both of them toss two coins sequentially, first Santa tosses a coin then Banta and so on. Santa tosses a fair coin: ...

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19

TIFR ECE 2013 | Question: 19
Which of the following is true for polynomials defined over real numbers $\mathbb{R}$. Every odd degree polynomial has a real root. Every odd degree polynomial has at least one complex root. Every even degree polynomial has at least one complex root. Every even degree polynomial has a real root. None of the above

Which of the following is true for polynomials defined over real numbers $\mathbb{R}$.Every odd degree polynomial has a real root.Every odd degree polynomial has at least...

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20

TIFR ECE 2013 | Question: 20
A function $f: \mathbb{R} \rightarrow \mathbb{R}$ is convex if for $x, y \in \mathbb{R}, \alpha \in[0,1], f(\alpha x+(1-\alpha) y) \leq \alpha f(x)+(1-\alpha) f(y)$. Which of the following is not convex: $x^{2}$ $x^{3}$ $x$ $x^{4}$ $\mathrm{e}^{x}$

A function $f: \mathbb{R} \rightarrow \mathbb{R}$ is convex if for $x, y \in \mathbb{R}, \alpha \in[0,1], f(\alpha x+(1-\alpha) y) \leq \alpha f(x)+(1-\alpha) f(y)$.Which...

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