AC Machines – Objective Questions

 

📘 AC Machines – Objective Questions 

Unit 2 – Single‑Phase Induction Motor

  1. Single‑phase induction motors are not self‑starting ✅

  2. Double revolving field theory explains: Starting of single‑phase induction motor ✅

  3. Split‑phase motor uses: Auxiliary winding with resistance ✅

  4. Capacitor start motor has: High starting torque ✅

  5. Shaded pole motor is used in: Fans and small appliances ✅

  6. Equivalent circuit of single‑phase induction motor is similar to: Transformer equivalent circuit ✅

  7. Slip in induction motor is: (Ns−N)/Ns ✅

  8. Applications of single‑phase induction motor: Ceiling fan, mixer, pump ✅

  9. Capacitor start‑capacitor run motor has: Better efficiency and power factor ✅

  10. Torque‑speed characteristic of single‑phase induction motor is: Non‑linear ✅

Unit 3 – Alternators

  1. Alternators are also called: Synchronous generators ✅

  2. EMF equation of alternator: E=4.44fNΦKcKb ✅

  3. Salient pole alternators are used in: Hydro power plants ✅

  4. Cylindrical rotor alternators are used in: Thermal power plants ✅

  5. Synchronous speed formula: Ns=120f/P ✅

  6. Armature reaction depends on: Power factor of load ✅

  7. Voltage regulation is determined by: Synchronous impedance method ✅

  8. Synchronization of alternator is done by: Lamp method or synchroscope ✅

  9. Infinite bus bar means: Constant voltage and frequency source ✅

  10. Chording factor reduces: Harmonics in EMF ✅

Unit 4 – Synchronous Motor

  1. Synchronous motor runs at: Constant synchronous speed ✅

  2. Synchronous motor is not self‑starting ✅

  3. V‑curve shows relation between: Armature current and field excitation ✅

  4. Inverted V‑curve shows: Power factor variation with excitation ✅

  5. Hunting in synchronous motor is: Oscillation of rotor ✅

  6. Hunting can be prevented by: Damper windings ✅

  7. Synchronous motor can operate at: Leading power factor ✅

  8. Leading power factor operation is used for: Power factor correction ✅

  9. Applications of synchronous motor: Constant speed drives, synchronous condenser ✅

  10. Torque in synchronous motor is due to: Interaction of rotor and stator fields ✅

Unit 5 – Special Electrical Machines

  1. Stepper motor rotates in: Discrete steps ✅

  2. Step angle of stepper motor depends on: Number of stator and rotor teeth ✅

  3. AC servo motor is used in: Control systems ✅

  4. Linear induction motor produces: Linear motion ✅

  5. Reluctance motor runs on: Variable reluctance principle ✅

  6. Hysteresis motor has: Uniform torque ✅

  7. Universal motor can run on: AC and DC supply ✅

  8. Universal motor is used in: Mixers, drills, sewing machines ✅

  9. Servo motors are used for: Precise control of position ✅

  10. Stepper motor is widely used in: Printers and CNC machines ✅

Mixed Numerical/Conceptual MCQs

  1. If supply frequency = 50 Hz and poles = 4, synchronous speed = 1500 rpm ✅

  2. If synchronous speed = 1500 rpm and rotor speed = 1470 rpm, slip = 2% ✅

  3. An alternator with 6 poles at 50 Hz has speed = 1000 rpm ✅

  4. A synchronous motor with 2 poles at 60 Hz runs at = 3600 rpm ✅

  5. Voltage regulation of alternator is positive if: Lagging power factor load ✅

  6. Voltage regulation of alternator is negative if: Leading power factor load ✅

  7. Step angle of stepper motor with 200 steps/rev = 1.8° ✅

  8. In synchronous motor, torque angle increases with: Load ✅

  9. In alternator, EMF increases with: Flux and speed ✅

  10. In induction motor, torque is proportional to: Slip at low values ✅

Comments

Post a Comment

Popular posts from this blog

Assignment – Control Systems (Unit 1)

   Assignment – Control Systems (Unit 1) Course: Electrical Engineering Semester: 4 Subject: Control Systems Assignment No.: 01 Maximum Marks: 20 Submission Date: 12/02/2026 Instructions Answer all questions neatly with proper diagrams wherever required. Use standard notation and units. Each question carries equal marks unless specified. Show all steps in derivations and numerical problems. Part A – Short Answer Questions (2 Marks Each) Differentiate between open-loop and closed-loop control systems with suitable examples. Define linear and nonlinear systems. Give one practical example of each. Explain the difference between time-variant and time-invariant systems. Define feedback in control systems. Why is it essential? Differentiate between degenerative (negative) and regenerative (positive) feedback. Part B – Long Answer Questions (Any two) (5 Marks Each) Derive the transfer function of an R-C circuit using Laplace transform. Derive the transfer function of ...
Read more

Assignment – AC Machines (Unit 1)

  Assignment – AC Machines (Unit 1) Course: Electrical Engineering Semester: 4 Subject: AC Machines Assignment No.: 01 Maximum Marks: 20 Submission Date: 27/02/2026 Instructions Answer all questions neatly with proper diagrams wherever required. Use standard notation and units. Each question carries equal marks unless specified. Show all steps in derivations and numerical problems. Part A – Short Answer Questions (2 Marks Each) Explain with neat and clean diagram the Construction and working principle of a three-phase induction motor. Define Slip and slip speed . Explain their significance. Explain Types of three phase induction motors . Draw Equivalent circuit of three phase induction motor and explain its components. Explain Rotor resistance starter – Why is it suitable for slip ring motors? Part B – Long Answer Questions (5 Marks Each) Compare squirrel cage and slip ring induction motors in terms of construction, performance, starting methods, and applications. Explain...
Read more

Assignment 02– Control System & PLC

  Assignment – Control System & PLC  Course: Electrical Engineering Semester: 4 Subject: Control System & PLC **Assignment No.: 02 Maximum Marks: 20 Submission Date: 22/04/2026 Instructions Answer all questions neatly with proper diagrams wherever required. Use standard notation and units. Each question carries equal marks unless specified. Show all steps in derivations and numerical problems. Part A – Short Answer Questions (Any five) (2 Marks Each) Explain the difference between open‑loop and closed‑loop control systems with examples. Define transfer function and explain its importance in system analysis. State the advantages of frequency response analysis over time domain analysis. What is the significance of block diagram reduction in control systems? List the advantages of PLCs compared to conventional relay logic. Explain the role of timers and counters in PLC programming. Write a simple ladder logic program for a lamp controlled by a switch. Part B –...
Read more