Recent questions tagged impedance

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GATE ECE 2020 | Question: 13
The impedances $Z=jX,$ for all $X$ in the range $\left ( -\infty ,\infty \right )$, map to the Smith chart as a circle of radius $1$ with centre at $(0, 0)$. a point at the centre of the chart. a line passing through the centre of the chart. a circle of radius $0.5$ with centre at $(0.5, 0)$.

asked Feb 13, 2020 in Electromagnetics by jothee (1.8k points) | 35 views

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GATE ECE 2020 | Question: 21
A transmission line of length $3\lambda /4$ and having a characteristic impedance of $50$ $\Omega$ is terminated with a load of $400 \Omega$. The impedance (rounded off to two decimal places) seen at the input end of the transmission line is __________ $\Omega$.

asked Feb 13, 2020 in Electromagnetics by jothee (1.8k points) | 28 views

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GATE ECE 2020 | Question: 46
For a $2$-port network consisting of an ideal lossless transformer, the parameter $S_{21}$ (rounded off to two decimal places) for a reference impedance of $10 \Omega$, is __________.

asked Feb 13, 2020 in Electromagnetics by jothee (1.8k points) | 14 views

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GATE ECE 2016 Set 1 | Question: 25
The propagation constant of a lossy transmission line is $(2+j5) m^{-1}$ and its characteristic impedance is $(50+j0) \Omega$ at $\omega = 10^6 rad \: s^{-1}$ ... $L = 250 \: \mu H/m, C = 0.2 \: \mu F/m, R=50 \: \Omega /m, \: G=0.04 \: S/m$

asked Mar 28, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 28 views

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GATE ECE 2016 Set 1 | Question: 31
A network consisting of a finite number of linear resistor (R), inductor (L), and capacitor (C) elements, connected all in series or all in parallel, is excited with a source of the form ... $\sum_{k=1}^{3} a_k\cos(k\omega_0t+\phi_k) \\$ $\sum_{k=1}^{2} a_k\cos(k\omega_0t+\phi_k)$

asked Mar 28, 2018 in Analog Circuits by Milicevic3306 (15.8k points) | 23 views

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GATE ECE 2015 Set 3 | Question: 53
Consider the $3\:m$ long lossless air-filled transmission line shown in the figure. It has a characteristic impedance of $120\pi\: \Omega,$ is terminated by a short circuit, and is excited with a frequency of $37.5\: MHz.$ What is the nature of the input impedance $(Z_{in})?$ Open Short Inductive Capacitive

asked Mar 28, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 17 views

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GATE ECE 2014 Set 4 | Question: 11
If the emitter resistance in a common-emitter voltage amplifier is not bypassed, it will reduce both the voltage gain and the input impedance reduce the voltage gain and increase the input impedance increase the voltage gain and reduce the input impedance reduce both the voltage gain and the input impedance

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 10 views

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GATE ECE 2014 Set 4 | Question: 24
For an antenna radiating in free space, the electric field at a distance of $1$ km is found to be $12 \: mV/m$. Given that intrinsic impedance of the free space is $120 \pi \: \Omega$, the magnitude of average power density due to this antenna at a distance of $2$ km from the antenna (in $nW/m^2$) is _________.

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 22 views

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GATE ECE 2014 Set 4 | Question: 33
For the two-port network shown in the figure, the impedance (Z) matrix (in $\Omega$) is $\begin{bmatrix} 6 & 24 \\ 42 & 9 \end{bmatrix}$ $\begin{bmatrix} 9 & 8 \\ 8 & 24 \end{bmatrix}$ $\begin{bmatrix} 9 & 6 \\ 6 & 24 \end{bmatrix}$ $\begin{bmatrix} 42 & 6 \\ 6 & 60 \end{bmatrix}$

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 7 views

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GATE ECE 2014 Set 3 | Question: 25
In the following figure, the transmitter $Tx$ sends a wideband modulated $RF$ signal via a coaxial cable to the receiver $Rx$. The output impedance $Z_{T}$ of $Tx$, the characteristic impedance $Z_{0}$ of the cable and the input impedance ... $Z_{R}\neq Z_{0}$ Impedance mismatches do NOT result in signal distortion but reduce power transfer efficiency

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 10 views

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GATE ECE 2014 Set 3 | Question: 32
In the circuit shown in the figure, the angular frequency $\omega$ (in rad/s), at which the Norton equivalent impedance as seen from terminals $b-b'$ is purely resistive, is ________.

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 11 views

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GATE ECE 2014 Set 2 | Question: 24
To maximum power transfer, a lossless transmission line is to be matched to a resistive load impedance via a $\lambda/4$ transformer as shown. The characteristic impedance (in $\Omega$) of the $\lambda$/4 transformer is ___________.

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 16 views

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GATE ECE 2014 Set 2 | Question: 54
In the transmission line shown, the impedance $Z_{\text{in}}$ (in ohms) between node A and the ground is _________.

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 16 views

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GATE ECE 2014 Set 1 | Question: 11
A good current buffer has low input impedance and low output impedance low input impedance and high output impedance high input impedance and low output impedance high input impedance and high output impedance

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 19 views

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GATE ECE 2014 Set 1 | Question: 54
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 halving of $v$ and no change in $Z$ no changes in $v$ and halving of $Z$ no change in both $v$ and $Z$ halving of both $v$ and $Z$

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 17 views

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GATE ECE 2014 Set 1 | Question: 55
The input impedance of a $\dfrac{\lambda}{8}$ section of a lossless transmission line of characteristic impedance $50\: \Omega$ is found to be real when the other end is terminated by a load $Z_{L} (=R + jX)\Omega.$ If $X$ is $30\:\Omega ,$ the value of $R ( \text{in} \:\Omega )$ is _______.

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 18 views

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GATE ECE 2013 | Question: 23
A source $v_{s}(t) = V\cos100\:\pi t$ has an internal impedance of $(4 + j3)\:\Omega.$ If a purely resistive load connected to this source has to extract the maximum power out of the source, its value in $\Omega$ should be $3$ $4$ $5$ $7$

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 18 views

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GATE ECE 2013 | Question: 15
In a voltage-voltage feedback as shown below, which one of the following statements is TRUE if the gain $k$ is increased? The input impedance increases and output impedance decreases The input impedance increases and output ... also increases The input impedance decreases and output impedance also decreases The input impedance decreases and output impedance increases

asked Mar 26, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 18 views

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GATE ECE 2012 | Question: 21
The impedance looking into nodes $1$ and $2$ in the given circuit is $50\:\Omega$ $100\:\Omega$ $5\:k\Omega$ $10.1\:k\Omega$

asked Mar 25, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 17 views

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GATE ECE 2012 | Question: 16
A coaxial cable with an inner diameter of $1\:mm$ and outer diameter of $2.4\:mm$ is filled with a dielectric of relative permittivity $10.89$. Given $\mu_0=4\pi\times10^{-7}\:H/m$, $\varepsilon_0=\frac{10^{-9}}{36\pi}\:F/m$, the characteristic impedance of the cable is $330\:\Omega$ $100\:\Omega$ $143.3\:\Omega$ $43.4\:\Omega$

asked Mar 25, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 14 views

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GATE ECE 2012 | Question: 10
The average power delivered to an impedance $(4-j3)\:\Omega$ by a current $5\cos(100\pi t+100)\:A$ is $44.2\:W$ $50\:W$ $62.5\:W$ $125\:W$

asked Mar 25, 2018 in Electromagnetics by Milicevic3306 (15.8k points) | 11 views

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GATE ECE 2018 | Question: 21
A lossy transmission line has resistance per unit length $R=0.05\:\Omega/m.$ The line is distortionless and has characteristic impedance of $50\:\Omega.$ The attenuation constant (in $\text{Np/m}$, correct to three decimal places) of the line is ________.

asked Feb 19, 2018 in Electromagnetics by gatecse (1.5k points) | 37 views

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GATE ECE 2018 | Question: 10
The points $\text{P, Q, and R}$ shown on the Smith chart (normalized impedance chart) in the following figure represent: $\text{P: Open Circuit, Q: Short Circuit, R: Matched Load}$ $\text{P: Open Circuit, Q: Matched Load, R: Short Circuit}$ $\text{P: Short Circuit, Q: Matched Load, R: Open Circuit}$ $\text{P: Short Circuit, Q: Open Circuit, R: Matched Load}$

asked Feb 19, 2018 in Electromagnetics by gatecse (1.5k points) | 36 views

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GATE ECE 2018 | Question: 3
A good transimpedance amplifier has low input impedance and high output impedance high input impedance and high output impedance high input impedance and low output impedance low input impedance and low output impedance

asked Feb 19, 2018 in Electromagnetics by gatecse (1.5k points) | 34 views