Well friends...all of Us know the importance of Indian Engineering Services (IES), considering the individual, the Society and the Nation. We also know the hardship and the struggle we may need to face. So, without wasting time.....lets start with Indian Engineering Services (IES) EC 1998 Conventional Questions and Solutions.
(Friends, here I have skipped one or two questions. Because either those are from old syllabus or framed wrongly. And within the week, I will start uploading the Solutions, so be prepared..:))
(Friends, here I have skipped one or two questions. Because either those are from old syllabus or framed wrongly. And within the week, I will start uploading the Solutions, so be prepared..:))
Paper I
Q.1. (a): Show that a semiconductor has minimum conductivity at a given temperature when
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Q.1. (b): When the current through a Zener diode increases from 20 mA to 30 mA the voltage across it changes from 5.6 V to 5.65 V. What is the voltage across the Zener when the cur rent is 35 mA ?
Q.1. (c): A train of rectangular pulses, making excursions from zero to one volt, have a duration of 2 s and are separated by intervals of 10 s. Assume that the center of one pulse is located at t= 0 and obtain the trigonometric, Fourier series for this pulse train.
Q.1. (d): A white noise is applied to an RC low pass filter. What is power spectral density of the output noise and what is its average power?
Q.1. (e): Find i1, i2, and v in the circuit of Fig.
Q.1. (f): Synthesize the two Foster networks for
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Q.1. (g): If the magnetic flux density of a point in a region is 250 sin 120 xt az mWb/m, what is the curl of the electric field intensity?
Q.1. (h): With the input of
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to an amplifier, the measured output amplitude is 1 volt at 1 kHz and 1 mV at 600 Hz. If the amplifier input-output characteristics is given by
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Determine the out- put amplitudes at the other frequencies.
Q.2.(a): A certain homogeneous slab of lossless dielectric material is characterized by an electric susceptibility of 0.12 and carries a uniform flux density within it of 1.6 nC/m. Find the electric field intensity, the polarization, the average dipole moment if there are 2e19 dipoles per cubic meter and the voltage between two equipotential 2.54 cm apart.
Q.2. (b): Calculate the inductance of a toroid formed by surfaces p = 3cm, p = 5cm, z = 0, z = 1.5 cm, wrapped with 5000 turns of wire. The core has a magnetic material with ur = 6 (Do not use approximation in evaluating the flux).
Q.4. (a):
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Find f(0), f’(0), f”(0).
(Note: F (s) is the Laplace transform of f(t)). Q.4. (b): Find the system transfer function and unit impulse response of the second order difference equation given below assuming zero initial conditions:
y(nT) = x(nT) – 0.25y(nT–2T)
Q.5 (a): The switch closes in the circuit of Fig. 5 (a) at t = 0. Assuming a relaxed circuit at the time of switching, determine the current i for t > 0. Also find the voltage VL across the inductances for t > 0.
Q.5 (b): Find the Z-parameters of the two port in Fig. 5 (b).
Q.6 (a): Given that V = XY is a solution of Laplace’s equation, where X is a function of x alone and Y is a function of y alone, determine which of the following functions are also solutions:
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Q.6 (b): An air-filled rectangular wave guide of cross-section 5 cm x 2 cm is operating in the TE10 mode at a frequency of 4 GHz. Determine:
(i) the group velocity (ii) the guide wavelength (iii) the attenuation to be expected at a frequency which is 0.95 time the cut-off frequency (assuming the guide walls to be made of perfect conductors).
Q.7 (a): A voltmeter with an internal resistance of 4750 Ohm is used to measure the voltage across a resistance of 600 Ohm connected in series with a DC series of internal resistance 400 Ohm. What is the error in measurement?
Q.7 (b):The periodic voltage of the form shown in the Fig. 7 (b) is applied to (i) a true r.m.s. meter (ii) an “average-measuring” – “r.m.s. indicating” meter (iii) a “peak-measuring” – “r.m.s. indicating” meter. Determine the reading of each instrument.
Paper II
Candidates should attempt Question 1 which is compulsory and four more questions
taking Two each from Section A and Section B.
Q.1. (a): A silicon transistor with VBE (sat) = 0.8 V, hFE = 100, VCE = 0.2 V is used in the circuit shown. Find the minimum value of RC(sat) for which the transistor remains in saturation.
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Q.1. (b): A silicon single phase full wave bridge rectifier circuit is shown. Explain what happens if the transformer and the load positions are interchanged.
Q.1. (d): The truth-table for A-B flip-flop is shown. Draw schematic diagram using J-K flip-flop and any additional logic to implement it. Show the design steps.
An Bn Qn+1
0 0 Qn
1 0 Qn
0 1 1
1 1 0
Q.1. (e): For open loop transfer function
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a negative feedback is applied with a feedback factor B. Find the value of A1,
(i) corresponding to the breakaway point,
(ii) for which the system becomes unstable.
Q.1. (f): According to CCIR system B standard for TV given the values of the following parameters: (i) Channel B.W (ii) Number of lines per picture (iii) Aspect ratio (iv) Line period (v) Field period.
Q.1. (g): Calculate the efficiency of a system which selects one message out of 13 equiprobable messages in (i) binary systems and (ii) decimal systems.
Q.1. (h): The terminating load of an HF transmission line with Z0 = 50 ohms working at 300 MHz is (50 +j50) ohms. Calculate the VSWR and the position of voltage minima nearest to the load.
Q.1. (i): An optical fibre has a core refractive index of 1.5 and a cladding refractive index of 1.47. Find
(i) Critical angle at core-cladding interface.
(ii) Numerical aperture NA of the fibre.
(iii) The acceptance angle in air for the fibre .
Q.1. (j): Define the following terms used in microprocessors:
(i) Instruction Cycle (ii) Machine Cycle (iii) T-State
Q.2. (a): Calculate Ri, Av and Ai for the circuit shown. Use hie = 100 Ohms, hfe = 99, hie = hoe = 0.
Q.2. (b): An amplifier with open loop voltage gain A = 1000 ± 100 is available. It is required to have an amplifier whose gain varies by no more than ± 0.2 %. Find (i) reverse transmission factor B of the feedback network (ii) gain with feedback. Derive the formula you used.
Q.3. (a): Develop the voltage transfer function V0/VS for the amplifier shown.
Q.3. (b): Explain the current foldback characteristics of voltage regulators. Draw a circuit to realize the current foldback characteristic in a low voltage regulator using 723 IC chip. Explain the working of the circuit.
Q.4. (a): Minimise the following logic expression using Karnaugh map.
f(A, B, C, D,E, F) = ∑m(6, 9, 13, 18, 19, 25, 27, 29, 41, 45, 57, 61)
Q.4. (b): A Tri-state logic gate circuit is shown. Explain the working of the circuit when (i) control is LOW and when (ii) control is HIGH. What are the applications of the circuit?
Q.4.(c): What is wired logic ? What are the applications of open collector TTL gates? For the circuit shown find expression for Y. What logical function is performed by the circuit?
Q.6. (a): A signal is band limited to 3.6 KHz and three other signals are band limited to 1.2 KHz each. These signals are to be transmitted by means of Time-Division-Multiplexing.
(i) If each signal is sampled at its Nyquist rate set up a scheme to achieve this multiplexing.
(ii) Specify the speed of commutator in samples per second.
(iii) If the commutator output is quantized in 1024 levels with the result binary coded, what is the output bit rate?
(iv) Determine the minimum transmission bandwidth of the channel.
Q.6. (b): Draw refractive index profile for
(i) step-index and
(ii) graded-index fibres.
Determine the cutoff wavelength for a step index fibre to exhibit single mode operation when the core refractive index and radius are 1.46 and 45 m respectively with the relative index difference being 0.25%.
Q.7. (a): A two stage amplifier has the following parameters:
First stage Second stage
Voltage gain 12 20
Input resistance 500 ohms 80 K ohms
Equivalent Noise Resistance 1500 ohms 10 K ohms
Output Resistance 25 K ohms 1 M ohms
Calculate:
(i) the equivalent noise resistance of the two stage amplifier;
(ii) the-noise figure of the amplifier if it is driven by a generator with, output impedance 50 ohms.
Q.7. (b): Explain Neutralization and show how it can be realized.
The circuit shown has an internal and stray wiring capacitance of 20 pF. If L1 = 80 mH and
L2 = 120 mH, determine to what value the neutralizing capacitance CN should be set so as to neutralize Cinternal.
Q.8. (a): For (6,3) systematic linear block code, the three parity-check bits C4, C5 and C6 are formed from the following equation C4 = d1 ⊕ d3 ; C5 = d1 ⊕ d2 ⊕ d3; C6 = d1 ⊕ d2
(i) Write the generator matrix G.
Q.8. (b): Calculate the ratio of circular waveguide cross-sectional area to the rectangular waveguide cross-sectional area assuming that both these waveguides have equal cutoff frequency for the dominant mode, if P11 = 1.841
Q.9. (b): Derive the major differences between the HDTV System and the NTSC System.
Q.8. (a): For (6,3) systematic linear block code, the three parity-check bits C4, C5 and C6 are formed from the following equation C4 = d1 ⊕ d3 ; C5 = d1 ⊕ d2 ⊕ d3; C6 = d1 ⊕ d2
(i) Write the generator matrix G.
(ii) Construct all possible code words.
(iii) If the received work is 010111 find the location of the error and the transmitted data bits.
Q.8. (b): Calculate the ratio of circular waveguide cross-sectional area to the rectangular waveguide cross-sectional area assuming that both these waveguides have equal cutoff frequency for the dominant mode, if P11 = 1.841
Q.9. (a): Explain with the help of D flip-flops, SR flip-flops and logic gates the working of all Interrupts available in the Microprocessor 8085 CPU.
Q.9. (b): Derive the major differences between the HDTV System and the NTSC System.
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