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DUET 2019 PhD in Electronics Previous Queston Papers

Delhi University Entrance Test (DUET) 2019 PhD in Electronics Previous Queston Papers

This post was last modified on 19 June 2020

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DUET Last 10 Years 2011-2021 Question Papers With Answer Key || Delhi University Entrance Test conducted by the NTA

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DU PhD in Electronics

Topic:- DU_J19_PHD_ELEC

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An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap Eg =2.45 eV). Electrons scattered by the crystal move at a velocity of 4.4 x 10⁵ m/s. The scattered energy (in eV) of the electrons is [Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
- 1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is [Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
- 25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30° to the smooth face of a crystal and line B of ? = 0.92 Å gives a third order reflection maxima at an angle 60° from the face of same crystal, then the wavelength of line A is [Question ID = 14769]
1. 3.36 Å [Option ID = 29073]
2. 6.72 Å [Option ID = 29076]
3. 0.84 Å [Option ID = 29075]
4. 1.59 Å [Option ID = 29074]
Correct Answer :-
- 3.36 Å [Option ID = 29073]
If y = Keinß then the value of 'K' after normalization in the limits 0 to p is [Question ID = 15449]
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1. vp [Option ID = 31794]
2. 2/vp [Option ID = 31793]
3. vp [Option ID = 31795]
4. 1/v2p [Option ID = 31796]
Correct Answer :-
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- 2/vp [Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of wavemeter, which indicates [Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
- frequency of microwave signal is zero [Option ID = 29137]

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In a p-type Si sample the hole concentration is 8 × 10¹⁵ / cm³. The intrinsic carrier concentration is 4 x 10¹⁰ / cm³. The electron concentration is [Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 × 10¹⁰/cm³ [Option ID = 29062]
3. 1.5 × 10²⁵/cm³ [Option ID = 29063]
4. 2 x 10⁵/cm³ [Option ID = 29064]
Correct Answer :-
- zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K. Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with effective noise temperature 290 K. The best receiver to purchase is [Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-

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A silicon bar of 1µm long and 100 µm² in cross-sectional area is doped with 10¹⁷cm^-3 Phosphorus. The saturation velocity is 10⁷ cm/sec. The current at 300 K with 10V applied is [Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
- 1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 µm. Given, the relative permittivity of silicon, ?_r = 12.7 and the permittivity of free space e₀ = 8.85 × 10^-12F/m. The depletion capacitance of the diode per square meter is [Question ID = 14767]
1. 7.65 µF [Option ID = 29065]
2. 3 µF [Option ID = 29067]
3. 8.15 µF [Option ID = 29066]
4. 5.62 µF [Option ID = 29068]
Correct Answer :-
- 7.65 µF [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture (NA) of the fiber is [Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
- 0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n₁) = 1.45. If core diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is [Question ID = 14776]
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1. 6.70 x 10³ Hz [Option ID = 29103]
2. 1.67 x 10³ Hz [Option ID = 29101]
3. 3.35 x 10³ Hz [Option ID = 29102]
4. 1.83 x 10³ Hz [Option ID = 29104]
Correct Answer :-
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- 1.67 × 10³ Hz [Option ID = 29101]
A three level laser emits laser light near the centre of visible band. If E₂ - E ₁ = 2.36 eV then the wavelength of radiation is [Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
- 550 nm [Option ID = 29105]

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log(1+x) = [Question ID = 14750]
1. -(x - x²/2 + x³/3 - x⁴/4 +...) |x| < 1 [Option ID = 28997]
2. x + x³/3 + x⁵/5 + x⁷/7 + ... [Option ID = 29000]
3. 1 + x + x² + x³ + .. [Option ID = 28999]
4. x - x²/2 + x³/3 + x⁴/4 +... x < 1 [Option ID = 28998]
Correct Answer :-
- -(x - x²/2 + x³/3 - x⁴/4 +...) |x| < 1 [Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is [Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
- Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2 mm. The diameter of the beam at a distance of 1 km is approximately [Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
- 10 mm [Option ID = 29113]
A Si sample (n_i = 1.5 × 10¹⁰ atoms/cm³) is doped with 10¹⁷ As atoms/cm³. The position of E_f related to E_i is [Question ID = 14761]
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1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
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- 0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in [Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
- bi-direction [Option ID = 29129]

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A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one after another, without replacement. The probability that the selected set contains one red ball and two black balls is [Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
- 1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm² V^-1s^-1. The diffusion coefficient of electrons is [Question ID = 14765]
1. 36.22 cm²/s [Option ID = 29057]
2. 62.25 cm²/s [Option ID = 29059]
3. 32.76 cm²/s [Option ID = 29060]
4. 49.16 cm²/s [Option ID = 29058]
Correct Answer :-
- 36.22 cm²/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = p, the coefficient of (x - p)² is [Question ID = 15451]
1. 0.5 exp(p) [Option ID = 31802]
2. exp(p) [Option ID = 31801]
3. exp(p) - 1 [Option ID = 31804]
4. exp(p) + 1 [Option ID = 31803]
Correct Answer :-
- exp(p) [Option ID = 31801]
In the expression 6 + 8i = 10e^i?, the value of ? is, [Question ID = 14743]
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1. 85.16° [Option ID = 28971]
2. 53.13° [Option ID = 28972]
3. 36.16° [Option ID = 28970]
4. 13.13° [Option ID = 28969]
Correct Answer :-
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- 13.13° [Option ID = 28969]
In the interval [0,1] the equation x = cos x [Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
- exactly one solution [Option ID = 31799]

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Choose the correct match out of the following options given below Column I P. 2nd order DEs Q. Non-linear algebraic equations R. Linear algebraic equations S. Numerical integration [Question ID = 14754]

Column II 1. Newton - Raphson method 2. Gauss Elimination 3. Simpson's rule 4. Runge-kutta method
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
- P->4 Q->1 R->2 S->3 [Option ID = 29014]
Helical antenna has the following polarization [Question ID = 14788]
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1. linear [Option ID = 29149]
2. elliptical [Option ID = 29151]
3. circular [Option ID = 29150]
Correct Answer :-
- linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions in Part-II and choose the correct answer from the following options. Part-I K. Infrared region L. Ultraviolet visible region M. X-ray region N. Y-ray region [Question ID = 14775]

Part-II 1. Electron transition involving valance electrons 2. Nuclear transitions 3. Vibrational transitions of molecules 4. Transitions involving inner shell electrons
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
- K->3 L->1 M->4 N->2 [Option ID = 29097]

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The particular integral of d²y/dx² + y = cos²x is [Question ID = 14757]
1. 1/3 sin 2x [Option ID = 29027]
2. -1/3 cos 2x [Option ID = 29026]
3. -1/3 cos 2x [Option ID = 29025]
4. -1/3 sin 2x [Option ID = 29028]
Correct Answer :-
- -1/3 cos 2x [Option ID = 29025]
If the temperature at any point in space is given by T = xy + yz + zx, direction of T in the direction of vector 3i – 4k at the point (1,1,1) is [Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
3. [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
- -5/2 [Option ID = 29017]
Eigen values of the matrix [ 0 1 0 0 1 0 0 0 0 0 0 -2i 0 0 2i 0 ] are [Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
- 1,0,2,3 [Option ID = 29021]
? (x²y + xy³) dxdy equals to (limits 0 to 2) [Question ID = 14747]
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1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
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- 4/3 [Option ID = 28985]
The numerical solution of the equation f(x) = x + vx-3 = 0 can be obtained using Newton-Raphson method. If the starting value is x = 2 for the iteration, the value of x that is to be used in the next step is [Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
- 0.732 [Option ID = 29037]

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Given x = (1-2t)/(1-t), y = ct² param w.r.t x in terms of t only is [Question ID = 14745]
1. 2t(1-t)² [Option ID = 28979]
2. 2t(1-2t)² / (1-t) [Option ID = 28980]
3. t(1-2t)² / 2(1-t) [Option ID = 28977]
4. (1-2t) [Option ID = 28978]
Correct Answer :-
- t(1-2t)² / (1-t) [Option ID = 28977]
The value of Lim_x?8 ¹/_x³-2 [Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
- 1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (e_r = 3.9) thickness of 10 nm, V_th = 0.6 V and w = 25 µm, L = 1 µm and electron mobility in channel, µ = 200 cm²/V-s. The drain current at V_GS = 5 V and V_DS = 0.1 V is [Question ID = 14778]
1. 7.51 × 10^-4 A [Option ID = 29111]
2. 3.05 × 10^-5 A [Option ID = 29109]
3. 5.1 x 10^-6 A [Option ID = 29110]
4. 8 × 10^-5 A [Option ID = 29112]
Correct Answer :-
- 3.05 × 10^-5 A [Option ID = 29109]
For z⁶ + z³ + 1 = 0, the general solution is [Question ID = 14744]
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1. e^-4in/3 [Option ID = 28975]
2. [Option ID = 28976]
3. e^in/3 [Option ID = 28974]
4. e^2in/3 [Option ID = 28973]
Correct Answer :-
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- e^2in/3 [Option ID = 28973]
A small concentration of minority carriers is injected into a homogeneous Semiconductor crystal at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority carriers by a distance of 1 cm in 20 usec. The mobility (in cm² /v-sec) of carriers is [Question ID = 14768]
1. 5000 [Option ID = 29072]
2. 2000 [Option ID = 29069]
3. 4000 [Option ID = 29071]
4. 3000 [Option ID = 29070]
Correct Answer :-
- 2000 [Option ID = 29069]

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Let the continuous random variable X denote the current measured in a thin copper wire in milli amperes (mA). Assume that the range of X is 4.9 = x = 5.1 and f(x) = 5. The probability that a current is less than 5mA is [Question ID = 14748]
1. 0.4 [Option ID = 28990]
2. 0.2 [Option ID = 28992]
3. 0.5 [Option ID = 28989]
4. 0.3 [Option ID = 28991]
Correct Answer :-
- 0.5 [Option ID = 28989]
A transmission line has a characteristic impedance of 75 O and a resistance of 5 O/m. If the line is distortion less, the attenuation constant (in Np/m) is [Question ID = 14792]
1. 0.066 [Option ID = 29167]
2. 0.033 [Option ID = 29168]
3. 0.022 [Option ID = 29165]
4. 0.055 [Option ID = 29166]
Correct Answer :-
- 0.022 [Option ID = 29165]
A transmitting antenna with a 300 MHz carrier frequency produces 4 kW of power. If both antennas has unity power gain, the power received by another antenna at a distance of 2 km is [Question ID = 14791]
1. 8.44 mW [Option ID = 29161]
2. 4.4 µW [Option ID = 29163]
3. 11.8 mW [Option ID = 29162]
4. [Option ID = 29164]
Correct Answer :-
- 8.44 mW [Option ID = 29161]
The power in power meter is displayed as -25 dB, when connected at the output of 30 dB attenuator. The input power applied to this attenuator is [Question ID = 14789]
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1. 10.2 mW [Option ID = 29154]
2. 3.16 mW [Option ID = 29156]
3. 1.5 mW [Option ID = 29155]
4. 5 mW [Option ID = 29153]
Correct Answer :-
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- 5 mW [Option ID = 29153]
The short-circuit current delivered by a 10 cm by 10 cm photocell (with 100% quantum efficiency) illuminated by monochromatic light of 400 nm wavelength with a power density of 1000 W/m² is [Question ID = 14773]
1. 6.85A [Option ID = 29092]
2. 5A [Option ID = 29089]
3. 8.32A [Option ID = 29091]
4. 3.2A [Option ID = 29090]
Correct Answer :-
- 5A [Option ID = 29089]

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The recursion relation to solve x - e^-x using Newton Raphson method is [Question ID = 14758]
1. x_n+1 = e^-xn [Option ID = 29029]
2. x_n+1 = x_n-e^-xn [Option ID = 29030]
3. x_n+1 = (1+x_n)2 / (2e^-xn-1) [Option ID = 29032]
4. x_n+1 = (1+x_n) / (1+e^-Xn) [Option ID = 29031]
Correct Answer :-
- x_n+1 = (1+x_n) / (1+e^-Xn) [Option ID = 29031]
The temperature required to generate electron-hole pairs in silicon (E_g = 1.1 eV) is (given electron charge=1.6 × 10^-19 J, Boltzman constant k =1.38 × 10^-23 J/°K) [Question ID = 14764]
1. 1522 K [Option ID = 29053]
2. 4174 K [Option ID = 29056]
3. 8502 K [Option ID = 29055]
4. 1130 K [Option ID = 29054]
Correct Answer :-
- 1522 K [Option ID = 29053]
The source of microwaves in a microwave oven is [Question ID = 14786]
1. klystron [Option ID = 29141]
2. cyclotron [Option ID = 29144]
3. gyratron [Option ID = 29142]
4. magnetron [Option ID = 29143]
Correct Answer :-
- magnetron [Option ID = 29143]
The operating frequency of source in the microwave oven is [Question ID = 14787]
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1. 1.45 GHz [Option ID = 29146]
2. 4.45 GHz [Option ID = 29148]
3. 3.45 GHz [Option ID = 29145]
4. 2.45 GHz [Option ID = 29147]
Correct Answer :-
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- 2.45 GHz [Option ID = 29147]
The line width of a He-Ne laser is 0.01 nm and the cross-sectional area of the beam is 0.01 cm². If the output power is 1mW, the radiation intensity per unit wavelength (in Watt/cm³) is [Question ID = 14780]
1. 10^-8 [Option ID = 29118]
2. 10¹⁰ [Option ID = 29117]
3. 10⁸ [Option ID = 29119]
4. 10^-10 [Option ID = 29120]
Correct Answer :-
- 10¹⁰ [Option ID = 29117]

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The application of VSWR meter to measure [Question ID = 14784]
1. air pressure [Option ID = 29136]
2. light intensity [Option ID = 29134]
3. SWR [Option ID = 29133]
4. scattering parameter [Option ID = 29135]
Correct Answer:-
- SWR [Option ID = 29133]
The dependence of Doppler broadened line width of a laser transition on temperature, 7 is given as [Question ID = 14781]
1. 7 [Option ID = 29121]
2. 7² [Option ID = 29124]
3. T^-1/2 [Option ID = 29122]
4. 7^1/2 [Option ID = 29123]
Correct Answer :-
- T^1/2 [Option ID = 29123]
The return loss of a device is found to be 40 dB. The voltage standing wave ratio (VSWR) and magnitude of reflection coefficient are respectively [Question ID = 14790]
1. -1.02 and 0.1 [Option ID = 29158]
2. 1.02 and 0.01 [Option ID = 29159]
3. 2.44 and 0.02 [Option ID = 29160]
4. 0.81 and 0.1 [Option ID = 29157]
Correct Answer :-
- 1.02 and 0.01 [Option ID = 29159]

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This download link is referred from the post: DUET Last 10 Years 2011-2021 Question Papers With Answer Key || Delhi University Entrance Test conducted by the NTA

This post was last modified on 19 June 2020