Kerala State Electricity Board Sub Engineer Electrical Paper 2012
1. Thickness of insulation layer on the conductor in cables depends on :
(A) current to be carried (B) operating voltage
(C) power factor (D) both (A) and (B)
2. Radio interference from a fluorescent tube can be reduced by:
(A) connecting a small capacitor across starter terminals
(B) eliminating choke
(C) putting two tubes in parallel
(D) any of the above
3. A series resonant circuit has :
(A) zero power factor and maximum current
(B) unity power factor and maximum current
(C) unity power factor and minimum current
(D) zero power factor and minimum current
4. Rated breaking capacity of a circuit breaker is :
(A) product of breaking current and fault voltage
(B) product of rated symmetrical breaking current and related voltage
(C) product of rated breaking current and rated voltage
(D) product of rated symmetrical breaking current and fault voltage
5. Pulse width of a 555 monostable multi vibrator is :
(A) 0.69 RC (B) 1.1 RC (C) RC (D) none of these
6. A DOL starter is employed for starting motors is due to :
(A) 3.75 kW (B) 7.5 kW (C) 15 kW (D) 25 kW
7. The sparking at the brushes in a dc machine is due to :
(A) armature reaction (B) reactants voltage
(C) high resistance of carbon brushes (D) presence of commutators
8. When the secondary winding of a potential transformer is suddenly open circuited with primary winding excited :
(A) primary winding draws only the no load current
(B) large voltage is produced and rupture the insulation
(C) large voltage is produced and causes safety hazard to operating personal
(D) none of the above
9. A 1 mA ammeter has a resistance of 100…. The shunt resistance to convert it to a 1 A ammeter is :
(A) 100 (B) 0.1001 (C) 0.001 (D) 10000
10. An alternator is synchronized to a bus bar whose frequency is 50 Hz. The bulb of the synchronoscope flickers at a frequency of 5 Hz. The frequency of the alternator is :
(A) 55 Hz (B) 45 Hz (C) 55 Hz or 45 Hz (D) none of the above
11. A differential amplifier has a common mode gain of 0.02. It has +200 mV signals applied to
each of its inputs. The amplitude of output signal is :
(A) 4 mV (B) 0 V (C) 8 mV (D) 1 mV
12. Which motor is preferred when quick speed reversal is the main cosideration :
(A) synchronous motor (B) squirrel cage induction motor
(C) slip ring induction motor (D) dc motor
13. Large industrial consumers are supplied power at :
(A) 132 kV (B) 400 kV (C) 11 kV (D) 66 kV
14. Mixture used for filling around the earth electrode for having effective earthing is :
(A) coal-salt mixture (B) coal-lime mixture
(C) coal-sawdust mixture (D) coal-sand mixture
15. In a variable speed induction motor drive V/f is kept constant. The motor operates in the:
(A) constant torque mode (B) constant power mode
(C) constant slip mode (D) variable power mode
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