HPCL Important Questions and Answer | august exam question practice - Electrical4u

HPCL Important Questions and Answer ( ELECTRICAL )

Q1. The material filled in breather of transformer is 

a) Silica gel

b) Sulphuric acid 

c) SF6

d) Mineral oil

Q2. The power factor in a transformer 

a) is always unity

b) is always leading

c) is always lagging

d) depends on power factor of load

Q3. A silent pole synchronous motor is running at no load . its field current is switched off . the motor will

a) Come to a stop

b) continue to run at synchronous speed

c) continue to run at a speed slightly more than the synchronous speed 

d) continue to run at a speed slightly less than the synchronous speed

Q4. NO load current in a transformer 

a) lags behind the voltage by about 75

b) leads the voltage by about 75

c) lags behind the voltage by about 90

d) leads the voltage by about 90

Q5. In the transformer , following winding has got more cross - section area

a) low voltage winding 

b) high voltage winding 

c) primary winding 

d) secondary winding 

Q6. The maximum efficiency of a distribution transformer is 

a) at no load 

b) at 50% full load 

c) at 80% full load 

d) at full load 

Q7. For a transformer , operation at constant load current, maximum efficiency will occur at 

a) 0.8 leading power factor

b) 0.8 lagging power factor 

c) zero power factor 

d) unity power factor 

Q8. Which of the following protection is not normally provided on small distribution transformation ? 

a) over fluxing protection

b) Buchholz relay

c) over current protection 

d) All of the above 

Q9. When a synchronous motor is running at synchronous speed , the damper winding produces 

a) damping torque 

b) eddy current torque 

c) torque aiding the developed torque 

d) no torque 

Q10. Maximum permissible earth resistance at large power stations is 

a) 0.5 ohm 

b) 1 ohm 

c) 2 ohms

d) 8 ohms 

Q11. 3-Phase slip ring induction motor is always started with a 

a) starting winding 

b) squirrel cage winding 

c) non external resistance in rotor circuit 

d) full external resistance in rotor circuit 

Q12. The starting torque of slip-ring induction motor can be increased by 

a) adding resistance to the stator 

b) adding resistance to the motor 

c) adding resistance to stator as well as the rotor  

d) none of the above 

Q13. Maximum permissible earth resistance for buildings is 

a) 0.5 ohm

b) 1 ohm 

c) 2 ohms 

d) 8 ohms 

Q14. Filament lamps operate normally at a power factor of 

a) 0.5 lagging 

b) 0.8 lagging 

c) unity 

d) 0.8 leading 

Q15. The function of capacitor across the supply to the flourescent tube is primarily to 

a) stabilize the arc 

b) reduce the starting current 

c) improve the supply power factor 

d) reduce the noise 

Q16. Motor output in HP is equal to 

a) kW input * Efficiency / 0.746

b) kW input * 0.746/Efficiency

c) Efficiency * 0.746/kW input 

d) 0.746/ (kW input * Efficiency 

Q17. The emf induced in the primary of a transformer 

a) is in phase with the flux 

b) lags behind the flux by 90 degree 

c) is in phase oppositions to that of flux 

d) leads the flux by 90 degree 

Q18. Crawling in the induction motor is caused by 

a) low voltage supply or high loads 

b) friction developed  in the motor 

c) flux wave produced by a stator winding is not pure since wave 

d) none of these 

Q19. It is advisable to avoid line starting of induction motor and use starter because 

a) motor takes five to seven times its full load current 

b) it will pick up very high speed and many go out of step 

c) it will run in reverse direction 

d) starting torque is very high 

Q20. If any two phases for an induction motor are interchanged 

a) the motor will run in reverse direction 

b) the motor will run at reduced speed 

c) the motor will not run 

d) the motor will burn 

Q21.The power factor of an induction motor under no-load conditions will be closer to 

a) 0.2 lagging 

b) 0.2 leading 

c) 0.5 leading 

d) unity  

Q22. Size of a high speed motor as compared to low speed motor for the same HP will be 

a) bigger 

b) smaller 

c) same

d) any of the above 

Q23. if the rotor circuit of a squrel cage induction motor is open , the rotor will 

a) run at very high speed 

b) run at very low speed 

c) make noise 

d) not run 

Q24. The ABCD Constant of a short transmission line are 

a) A = Z , B =1 , C = 0 , D = 1

b) A = 0 , B = 1 , C = Z , D = 1

c) A = 1 , B = Z , C = 0 , D = 1 

d) A = 1 , B = 0 , C = 1 , D = Z 

Q25. The meter constant of a single phase 240 v induction watt hour meter is 400 revolutions per kWh . the speed of the meter disc for a current of 10 amp. of 0.8 power factor lagging will be 

a) 12.8 rpm

b) 16.02 rpm 

c) 18.2 rpm 

d) 21.1 rpm 

explanation 

K = 400 rev/kwh 

  = 400 rev / rpm 

power factor = ( 400 * 240 * 10 * 0.8 ) /( 1000 * 60 )

             = 12.8 rpm