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Electronics & Communication

1 A digital-to-analog converter with a full-scale output voltage of 3.5 V 
has a resolution close to 14m V. Its bit size is 
A) 4
B) 8
C) 16 

D) 32
Answer : (B)

2 A single-phase half-controlled 
rectifier is driving a separately excited dc motor. The dc motor has a back emf 
constant of 0.5 V/rpm. The armature current is 5 A without any ripple. The 
armature resistance is 2W. The converter is working from a 280 V, single phase 
ac source with a firing angle of 80°. Under this operating condition, the speed 
of the motor will be 
A) 339 rpm 
B) 359 rpm 
C) 366 rpm 
D) 386 
rpm
Answer : (C)

3 In relation to the synchronous machines, 
which one of the following statements is false? 
A) In salient pole 
machines, the direct-axis synchronous reactance is greater than the 
quadrature-axis synchronous reactance
B) The damper bars help the synchronous 
motor self start
C) Short circuit ratio is the ratio of the field current 
required to produce the rated voltage on open circuit to the rated armature 
current 
D) The V-curve of a synchronous motor represents the variation in 
the armature current with field excitation, at a given output power
Answer 
: (C)

4 A parallel plate air-filled capacitor has plate area of 
l0-4 m2 and plate separation of 10-3 m. It is connected to a 0.5 V, 3.6 GHz 
source. The magnitude of the displacement current is (e0 = 1/36p x 10-9 F/m) 

A) 10 mA
B) 100 mA
C) 10 A 
D) 1.59 mA
Answer : 
(A)

5 The 8085 assembly language instruction that stores the 
content of H and L registers into the memory locations 2050H and 2051H, 
respectively, is 
A) SPHL 2050_H 
B) 
SPHL2051_H
C) SHLD 2050_H
D) STAX 
2050_H
Answer : (C)

6 If E is the electric field 
intensity, Ñ(Ñ x E ) is equal to 
A) E 
B) | E |
C) null vector 

D) zero
Answer : (D)

7 The insulation strength of an EHV 
transmission line is mainly governed by
A) load power factor 
B) 
switching over-voltages
C) harmonics 
D) corona
Answer : (B)

Edited by Priya - 04Jan2007 at 4:29pm


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