#1
June 27th, 2016, 11:30 AM
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Delhi Metro Recruitment Question Papers
Hello sir I want to prepare for Delhi Metro Recruitment and here for practice can you please give me question paper ?
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#2
June 27th, 2016, 11:43 AM
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Re: Delhi Metro Recruitment Question Papers
Hey as per your demand here I am providing you details of Delhi Metro Recruitment Question Paper for your practice Here I am giving you question paper 1. The ability of a material to remain magnetized after removal of the magnetizing force is known as Permeability reluctance hysteresis retentivity Ans 2. When a solenoid is activated, the force that moves the plunger is an electromagnetic field a permanent magnetic field varying voltage a steady current Ans:A 3. Which of the following capacitors is polarized mica ceramic plastic-film electrolytic Ans 4. In a series resonant band-pass filter, a lower value of Q results in a higher resonant frequency a smaller bandwidth a higher impedance a larger bandwidth Ans 5. A steady-state condition is reached when the output voltage reaches the average value of the input voltage the output voltage reaches the input voltage the output voltage reaches approximately 63% of the input voltage the output voltage reaches the effective value of the input voltage Ans:A 6. An RC differentiator acts as a low-pass filter high-pass filter band-pass filter band-stop filter Ans:B 7. A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is 1500 r.p.m. 1425 r.p.m. 25 r.p.m. 75 r.p.m. Ans Explanation: NS = 120f /P = 120 x 50 /4 =1500rpm N = NS ( 1-s) = 1500 (1-0.05) = 1425 \relative speed = 1500 – 1425 = 75 rpm 8. A ceiling fan uses split-phase motor. capacitor start and capacitor run motor universal motor. capacitor start motor. Ans 9. The drive motor used in a mixer-grinder is a dc motor. induction motor. synchronous motor. universal motor. Ans 10. A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals 0.2 Amp. 5 Amps 10 Amps. 20 Amps. Ans:A Explanation: I1= V1 /R1 = 120/600 = 0.2 (h = 100%, losses are zero \V1 = VR = I1R1) 11. A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles of the motor are 4. 6. 12 8. Ans:A Explanation: N= Ns (1-S) = NS –NS x S 1440 = Ns (1-S) Ns = 1440 / (1-S) Ns = (120 f/ p) = 120 x 50/p = 6000 p Ns will be closer to N i.e 1440 When P=2 ; Ns = 3000 rpm , not close to N When P=4 ; Ns = 1500 rpm , it is closer to N Therefore P =4 for N=1440 12. In a 3-phase synchronous motor the speed of stator MMF is always more than that of rotor MMF. the speed of stator MMF is always less than that of rotor MMF. the speed of stator MMF is synchronous speed while that of rotor MMF is zero rotor and stator MMF are stationary with respect to each other. Ans Explanation: Because, Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction Therefore, rotor & stator mmf are stationary w.r.t each other. 13. In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. delta side lags by -30°. star side lags by -30°. delta side leads by 30°. star side leads by -30°. Ans:C Explanation: This is vector group and has +30° displacement. Therefore, delta side leads by +30°. 14. Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf? 10 Hz. 50 Hz. 1 Hz. 2500 Hz. Ans:C Explanation: Given : s = 0.02 ; f = 50 Hz Therefore, frequency of rotor induced emf = s f = 0.02 x 50 = 1.0 Hz 15. A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf? 100 Volts. 0.1 Volts. 1 Volts. 10 Volts. Ans Explanation: Given N = 1500 rpm, F = 0.4 mWb, Z = 1000, P = 4, & A= 4 Therefore, Eb = NFPZ / 60 A = 1500 x 0.4 x 4 x 1000 x 10-3 / 60 x 4 = 60/6 = 10 volts |
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