Formula for Number of Magnetic poles (P) in an Induction motor= ____ 

This question was previously asked in
RRB ALP CBT 2 Electronic Mechanic Previous Paper: Held on 23 Jan 2019 Shift 1
View all RRB ALP Papers >
  1. (180 × f)/N
  2. (60 × f)/N
  3. (360 × f)/N
  4. (120 × f)/N

Answer (Detailed Solution Below)

Option 4 : (120 × f)/N
Free
General Science for All Railway Exams Mock Test
2.1 Lakh Users
20 Questions 20 Marks 15 Mins

Detailed Solution

Download Solution PDF

Concept:

In a three-phase induction motor, the number of magnetic poles depends upon the  supply frequency and the synchronous speed as follows:

\({P} = \frac{{120f}}{N}\)

Where P = number of poles

N = Synchronous Speed in rpm

f = supply frequency in Hz

26 June 1

  • The number of poles or the number of magnetic poles refers to the magnetic poles (NSNS…) that appear on the surface created by cutting the motor perpendicularly to the shaft.
  • Synchronous speed is the speed of rotation of the magnetic field in a rotary machine. An induction motor always runs at a speed less than synchronous speed.
Latest RRB ALP Updates

Last updated on Jun 11, 2025

-> The RRB NTPC Admit Card 2025 has been released on 1st June 2025 on the official website.

-> The UPSC Prelims Result 2025 and UPSC IFS Result 2025 has been released @upsc.gov.in

-> Railway Recruitment Board activated the RRB ALP application form 2025 correction link, candidates can make the correction in the application form till 31st May 2025. 

-> The Railway Recruitment Board (RRB) has released the official RRB ALP Notification 2025 to fill 9,970 Assistant Loco Pilot posts.

-> The Railway Recruitment Board (RRB) has released the official RRB ALP Notification 2025 to fill 9,970 Assistant Loco Pilot posts.

-> The official RRB ALP Recruitment 2025 provides an overview of the vacancy, exam date, selection process, eligibility criteria and many more.

->The candidates must have passed 10th with ITI or Diploma to be eligible for this post. 

->The RRB Assistant Loco Pilot selection process comprises CBT I, CBT II, Computer Based Aptitude Test (CBAT), Document Verification, and Medical Examination.

-> This year, lakhs of aspiring candidates will take part in the recruitment process for this opportunity in Indian Railways. 

-> Serious aspirants should prepare for the exam with RRB ALP Previous Year Papers.

-> Attempt RRB ALP GK & Reasoning Free Mock Tests and RRB ALP Current Affairs Free Mock Tests here

More Induction Motor Slip Questions

Get Free Access Now
Hot Links: teen patti master 2024 teen patti download teen patti master gold apk teen patti dhani