One Stop GATE Forum: 1998- year EE GATE Paper

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1.  In each of sub question (1.1 to 1.22) four alternatives A, B, C and D are provided of which one is correct. Indicate in your book, at the space provided, the correct answer by writing the alphabet corresponding to the answer. 

1.1  A sinusoidal source of voltage V and frequency f is connected to a series circuit of 
variable  resistance,  R  and  a  fixed  reactance,  X.  The  locus  of  the  tip  of  the 
current-phasor, I, as R is varied from 0 to 8 is:   
V
X  
  (a)  a semicircle with a diameter of  .
  (b)  a straight line with a slop of  R
X  
  (c)  an ellipse with  V
R as major axis. 
V
˜ ’
  (d)  a circle of radius  R
. 
÷
X and origin at  0, 2
«  

1.2  The laws of electromagnetic induction (Faraday‘s and Lenz‘s law) are summarized in the following equation: 
  (a)  e = iR      (b)  di e Ldt
  (c)  de dt        (d)  None of the above 

1.3  A synchronous generator connected to an infinite bus is overexcited. Considering 
only  the reactive power, from  the point of view  of the system,  the machine  acts 
as 
  (a)  a capacitor      (b)  an inductor 
 (c)  a resistor      (d)  None of the above 

1.4  A  3  phase  squirrel  cage  induction  motor  has  a  full  load  efficiency  of  0.8  and  a 
maximum  efficiency of 0.9.  It is  operated  at a  slip of 0.6  by applying  a reduced 
voltage. The efficiency of the motor at this operating point is: 
  (a)  less than 0.4      (b)  greater than 0.6   
 (c)  in the range of 0.8 ±0.1  (d)  None of the above 

1.5  The  efficiency  of  a 100  KVA  transform  is 0.98 at  full  as well  as at  half  load. For 
this transformer at full load the copper loss. 
  (a)  is less than core loss    (b)  is equal to core loss 
 (c)  is more than core loss   (d)  None of the above 

1.6  The magnetizing current in a transformer is rich in 
 (a)  3r d harmonic  (b)  5th harmonic  (c)  7t h harmonic  (d) 13th harmonic 

1.7  Series capacitive compensation in EHV transmission lines is used to 
 (a)  reduce the line loading   
 (b)  improve the stability of the system   
 (c)  reduce the voltage profile  (d)  improve the protection of the line 

1.8  Bulk power transmission over long HVDC lines are preferred, on account of 
 (a)  low cost of HVDC terminals  (b)  no harmonic problems  
 (c)  minimum line power losses  (d)  simple protection 

1.9  None of  the poles of a linear  control system lie in  the right half of s-plane. For a 
bounded input, the output of this system 
  (a)  is always bounded    (b)  could be unbounded   
 (c)  always tends to zero    (d)  None of the above 

1.10  The phase lead compensation is used to   
 (a)  increase rise time and decrease overshoot   
 (b)  decrease both rise time and overshoot   
 (c)  increase both rise time and overshoot   
 (d)  decrease rise time and increase overshoot 

1.11  A  set  of  linear  equations  is  represented  by  the  matrix  equation  Ax=b.  the 
necessary condition for the existence of a solution for this system is:   
  (a)  A must be invertible   
 (b)  b must be linearly depended on the columns of A   
 (c)  b must be linearly independent of the columns of A   
 (d)  None of the above 

1.12  A d.c. voltmeter has a sensitivity of 1000  /volt. When it measures half full scale 
in 100V range, the current through the voltmeter is 
  (a)  100 mA  (b)  1 mA  (c)  0.5 mA  (d) 50 mA 

1.13.  A moving coil galvanometer is made into a d.c. ammeter by connecting 
 (a)  a low resistance across the meter   
 (b)  a high resistance in series with the meter   
 (c)  a pure inductance across the meter   
 (d)  a capacitor in series with the meter 

1.14.  The  open  collector  outputs  of  two  2-inputs  NAND  gates  are  connected  to  a 
common pull up resistor. If the input to the gates are P, Q and R, S respectively, 
the output is equal to 
  (a)  . . . .
PQ R S   (b)  PQ RS
+   (c)  . .
PQ R S
+   (d)  .  .  .
PQ R S 

1.15.  In standard TTL gates, the totem pole output stage is primarily used to 
 (a)  increase the noise margin of the gate       
 (b)  decrease the output switching delay 
 (c)  facilitate a wired OR logic connection       
 (d)  increase the output impedance of the circuit 

1.16.  One of the applications of current mirror is:  
 (a)  output current limiting   
 (b)  obtaining a very high current gain 
 (c)  current feedback 
 (d)  temperature stabilized biasing 

1.17.  The uncontrolled electronic switch employed in power electronic converters is: 
 (a)  thyristor      (b)  bipolar junction transistor   
 (c)  diode      (d)  MOSFET 

1.18.  The MOSFET switch in its on-state may be considered equivalent to: 
 (a)  resistor  (b)  inductor  (c)  capacitor  (d) battery 

1.19.  In  a  commutation  circuit  employed  to  turn  off  an  SCR,  satisfactory  turn-off  is 
obtained when 
  (a)  circuit turn-off time < device turn-off time       
 (b)  circuit turn-off time > device turn-off time 
 (c)  circuit time constant > device turn-off time       
 (d)  circuit time constant < device turn-off time   

 1.20.  The  neutral  of  10  MVA,  11  KV  alternator  is  earthed  through  a  resistance  of  5 
1H 
3H 
 5H 
2H 
B 
 6H 
ohms.  The  earth  fault  relay  is set  to  operate at  0.75A.  The  CT‘s have a  ratio  of 
1000 :5.What percentage of the alternator winding is protected? 
  (a)  85%   (b)  88.2%   (c)  15%  (d) 11.8% 

1.21.  If the length of a wire of resistance R is uniformly stretched to n times its original 
value, its new resistance is: 
  (a)  nR  (b)  R
n R   (d)  R
n   (c)  2
n2  

1.22.  A cable has the  following characteristics.  L  =0.201  H/m and C = 196.2  p/F/m. 
The velocity of wave propagation through the cable is: 
  (a)  32 m/s  (b)  159.24  /ms  (c)  0.0312 m/s  (d) 159.24 m/s 

Author	Message
Arpita Groupie Joined: 04Jan2007 Online Status: Offline Posts: 73	Topic: 1998- year EE GATE Paper Posted: 14Feb2007 at 10:15am
	1. In each of sub question (1.1 to 1.22) four alternatives A, B, C and D are provided of which one is correct. Indicate in your book, at the space provided, the correct answer by writing the alphabet corresponding to the answer. 1.1 A sinusoidal source of voltage V and frequency f is connected to a series circuit of variable resistance, R and a fixed reactance, X. The locus of the tip of the current-phasor, I, as R is varied from 0 to 8 is: V X (a) a semicircle with a diameter of . (b) a straight line with a slop of R X (c) an ellipse with V R as major axis. V ˜ ’ (d) a circle of radius R . ÷ X and origin at 0, 2 « 1.2 The laws of electromagnetic induction (Faraday‘s and Lenz‘s law) are summarized in the following equation: (a) e = iR (b) di e Ldt (c) de dt (d) None of the above 1.3 A synchronous generator connected to an infinite bus is overexcited. Considering only the reactive power, from the point of view of the system, the machine acts as (a) a capacitor (b) an inductor (c) a resistor (d) None of the above 1.4 A 3 phase squirrel cage induction motor has a full load efficiency of 0.8 and a maximum efficiency of 0.9. It is operated at a slip of 0.6 by applying a reduced voltage. The efficiency of the motor at this operating point is: (a) less than 0.4 (b) greater than 0.6 (c) in the range of 0.8 ±0.1 (d) None of the above 1.5 The efficiency of a 100 KVA transform is 0.98 at full as well as at half load. For this transformer at full load the copper loss. (a) is less than core loss (b) is equal to core loss (c) is more than core loss (d) None of the above 1.6 The magnetizing current in a transformer is rich in (a) 3r d harmonic (b) 5th harmonic (c) 7t h harmonic (d) 13th harmonic 1.7 Series capacitive compensation in EHV transmission lines is used to (a) reduce the line loading (b) improve the stability of the system (c) reduce the voltage profile (d) improve the protection of the line 1.8 Bulk power transmission over long HVDC lines are preferred, on account of (a) low cost of HVDC terminals (b) no harmonic problems (c) minimum line power losses (d) simple protection 1.9 None of the poles of a linear control system lie in the right half of s-plane. For a bounded input, the output of this system (a) is always bounded (b) could be unbounded (c) always tends to zero (d) None of the above 1.10 The phase lead compensation is used to (a) increase rise time and decrease overshoot (b) decrease both rise time and overshoot (c) increase both rise time and overshoot (d) decrease rise time and increase overshoot 1.11 A set of linear equations is represented by the matrix equation Ax=b. the necessary condition for the existence of a solution for this system is: (a) A must be invertible (b) b must be linearly depended on the columns of A (c) b must be linearly independent of the columns of A (d) None of the above 1.12 A d.c. voltmeter has a sensitivity of 1000 /volt. When it measures half full scale in 100V range, the current through the voltmeter is (a) 100 mA (b) 1 mA (c) 0.5 mA (d) 50 mA 1.13. A moving coil galvanometer is made into a d.c. ammeter by connecting (a) a low resistance across the meter (b) a high resistance in series with the meter (c) a pure inductance across the meter (d) a capacitor in series with the meter 1.14. The open collector outputs of two 2-inputs NAND gates are connected to a common pull up resistor. If the input to the gates are P, Q and R, S respectively, the output is equal to (a) . . . . PQ R S (b) PQ RS + (c) . . PQ R S + (d) . . . PQ R S 1.15. In standard TTL gates, the totem pole output stage is primarily used to (a) increase the noise margin of the gate (b) decrease the output switching delay (c) facilitate a wired OR logic connection (d) increase the output impedance of the circuit 1.16. One of the applications of current mirror is: (a) output current limiting (b) obtaining a very high current gain (c) current feedback (d) temperature stabilized biasing 1.17. The uncontrolled electronic switch employed in power electronic converters is: (a) thyristor (b) bipolar junction transistor (c) diode (d) MOSFET 1.18. The MOSFET switch in its on-state may be considered equivalent to: (a) resistor (b) inductor (c) capacitor (d) battery 1.19. In a commutation circuit employed to turn off an SCR, satisfactory turn-off is obtained when (a) circuit turn-off time < device turn-off time (b) circuit turn-off time > device turn-off time (c) circuit time constant > device turn-off time (d) circuit time constant < device turn-off time 1.20. The neutral of 10 MVA, 11 KV alternator is earthed through a resistance of 5 1H 3H 5H 2H B 6H ohms. The earth fault relay is set to operate at 0.75A. The CT‘s have a ratio of 1000 :5.What percentage of the alternator winding is protected? (a) 85% (b) 88.2% (c) 15% (d) 11.8% 1.21. If the length of a wire of resistance R is uniformly stretched to n times its original value, its new resistance is: (a) nR (b) R n R (d) R n (c) 2 n2 1.22. A cable has the following characteristics. L =0.201 H/m and C = 196.2 p/F/m. The velocity of wave propagation through the cable is: (a) 32 m/s (b) 159.24 /ms (c) 0.0312 m/s (d) 159.24 m/s
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