A) revolving rotor
B) air gap between rotor and stator
C) higher flux densities in induction motor
D) none of the above
✅ Answer:
➡️ B) air gap between rotor and stator
🧠Detailed Solution
◆ Step 1: Key Concept
➡️ Induction motor is like a generalized transformer
➡️ But with one major difference → air gap present
◆ Step 2: Compare Magnetic Circuits
Transformer:
→ No air gap
→ Low reluctance
→ Flux is tightly coupled
Induction Motor:
→ Has air gap between stator & rotor
→ High reluctance
→ Flux spreads more
◆ Step 3: Effect of Air Gap
➡️ Due to air gap:
→ Magnetizing current increases
→ Flux lines are not tightly confined
→ Leakage flux increases
◆ Step 4: Practical Observation
→ Induction motor no-load current = 30–60% of rated
→ Transformer no-load current = 2–6%
➡️ Reason: higher leakage + magnetizing requirement
❌ Why Other Options Are Incorrect
◆ A) revolving rotor → Not main cause
◆ C) higher flux density → Not correct reason
◆ D) none → Incorrect
🔑 Key Points to Remember
◆ Air gap ⇒ High reluctance
◆ High reluctance ⇒ More leakage flux
◆ Induction motor behaves like transformer with air gap
◆ Poorer coupling than transformer
🎯 Final Conclusion
➡️ Leakage flux is higher due to:
Air gap between stator and rotor ✔️