ENGINEERING CAREER AND STUDY MATERIALS

Question No. 1. The d.c. series motor should always be started with load because (A) at no load, it will rotate at dangerously high speed. (B) it will fail to start. (C) it will not develop high starting torque. (D) all are true.  Ans: A Question No. 2. The armature of a dc machine is laminated to reduce: (A) Eddy current loss (B) Hysteresis loss (C) copper losses (D) friction and windage losses  Ans: A Question No. 3. The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero.  Ans: C Question No. 4. If a single phase alternator has 8 slots per pole uniformly speed, but the winding is arranged with the middle two left empty, the breadth coefficient will be (A) 0.53. (B) 0.88 (C) 0.67 (D) 0.99 Answer: (A) 0.53. Question No. 5. In DC generators, armature reaction is produced actually by  (A) Its field current. (B) Armature conductors.  (C...

Q1. The e.m.f. generated in a D.C. generator is directly proportional to (a) flux/pole (b) speed of armature (c) number of poles (d) all of the above Ans: b Q.2 In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.  Ans: C Q3. In a commutator (a) copper is harder than mica (b) mica and copper are equally hard (c) mica is harder than copper (d) none of the above Ans: c Q4. The emf generated due to nth harmonic component of flux in an alternator will be (A) n times the fundamental emf (B) same as fundamental emf (C) less than the value of fundamental emf. Q5. In a capacitor start single-phase induction motor, the capacitor is connected  (A) in series with main winding.  (B) in series with auxiliary winding.  (C) in series with both the windings.  (D) in parallel with auxiliary winding.  Ans: B Q6. The insulating mate...