### Discussion :: Alternating Current and Voltage - General Questions (Q.No.2)

Vineeta Verma said: (Jan 8, 2011) | |

f = pn/120 f = 400*60*2/120 f = 400 HZ |

Mahendra said: (Mar 3, 2011) | |

From where did the 60 came please tell me vineeta verma. |

Raj said: (Mar 3, 2011) | |

Because we have to change rps to rpm. |

Talha said: (May 7, 2011) | |

Thanks for that answer. |

Vipul Parmar said: (Aug 17, 2011) | |

F = PN/120 = 400*60*2/120 = 400Hz Because 400*60 rps= 400 rpm. |

Yanusha A said: (Sep 22, 2011) | |

N=120F/P N=400rps=400*60rpm p=2 F=NP/120 =400*60*2/120 =400HZ |

Sandeep said: (Nov 21, 2011) | |

P=2 N= 400 r/s (rps )= 400 r/(m/60)=400*60 r/m =400*60 rpm we know f = N P /120= 400*60*2/120=400 Hz. |

Mau Chau said: (Feb 16, 2012) | |

Thanks raj. |

Bhavesh said: (Mar 13, 2012) | |

Sandip your answer is correct. |

Pukhraj said: (Mar 17, 2012) | |

Thanks vineeta. |

Vinothkumar said: (Aug 28, 2012) | |

Thanks sandeep. |

Mustafa said: (Sep 3, 2012) | |

If this is a single phase generator , how are we considering the angle to be 120 degrees? |

Ribka A said: (Sep 15, 2012) | |

In three phase generators we will consider the angle between three coils should be 120 degrees. |

Amarendra Dash said: (Aug 28, 2013) | |

We know N = 120F/P. SO F = N*P/120. Here n = 400rps(revolution per second). n = 400*60rpm(rps=Hz=60*rpm). Thus, F = 400*60*2/120. F = 400Hz answer. |

Ahmed said: (Feb 13, 2014) | |

n= 120*f/p. n : rapid per minute. f: frequency. p:no of poles. n=400*60(rps) =24000(rpm). f=n(rpm)*p/120. f=24000*2/120. f=400 HZ. |

Thiru Punk said: (Apr 19, 2015) | |

n(rps) = 400 rps. p(pole) = 2. f = (pn/2). f = (2*400/2) => 400Hz. |

Ch Nikhil Chakravarthy said: (Apr 19, 2015) | |

Since f=1/T. Here f is frequency. T is time in seconds. |

Girishgowda said: (Jun 27, 2015) | |

p = 2. n = 400. rps its converted in to rpm its value is 6.66 rpm. Then f = pn/120. = 2*6.66/120. = 0.111 hz. |

Navya said: (Aug 20, 2015) | |

Where 1sec=1/60min. But how you multiplied 60 in the speed. |

Mrityunjay said: (Aug 20, 2015) | |

Please any one tell from where 2 is came? |

Kalai Sasi said: (Sep 26, 2015) | |

Its a number of poles. |

Jansi said: (Jan 24, 2016) | |

Here given data is: No. of poles = 2; Speed (N) = 400 rps; Usually speed is calculated in rpm. So here we convert 400 rps (revolution per second) in terms of rpm (revolutions per minute). As 1 min = 60 sec; we multiply 400x60 rpm; As we know N = 120f/p. f = np/120; f = 400x60x2/120. f = 400 hz. So hope no one has any doubts regarding this explanation. |

Rakshith said: (Aug 20, 2016) | |

As we all know, Ns = ( (120 * f) /p); Here Ns is in rpm. Therefore, Ns = Ns/60 rps. So, Ns = ((2 * f)/p), And f = ((p * ns)/2), f = 2 * 400/2, f = 400Hz. |

Hassan said: (Aug 29, 2016) | |

How did you guys get that 120? |

Fatima said: (Dec 13, 2016) | |

@Hassan. Formula contains Ns syncronous speed ,Ns = (( 120 * f ) /p). |

Bhanu said: (Feb 7, 2017) | |

Great job @Jansi. |

Waheed Ullah Khattak said: (Feb 16, 2017) | |

If we change RPS to RPM then we should have to divide by 60. |

Surya said: (Aug 16, 2017) | |

N= 120f/p. F= 400*60*2/120. F= 400. |

Sunnyleon said: (Oct 2, 2017) | |

Thank you @Sandeep. |

Kiran said: (Dec 7, 2017) | |

rps=400*60=24000=Ns. P=2 Ns=120f/p 120*f/Ns*p f=Ns*p/120 f=24000*2/120 f=400. |

Feroz Khan said: (May 10, 2018) | |

1rpm=60rps. so 1rps 1/60 rpm and, 400rps=400 * 1/60 rps. I think the answer is wrong @Kiran. |

D.Jyothi said: (Aug 30, 2018) | |

As per the definition, frequency means that the number of cycles completed by one rotation. |

Asim said: (Sep 2, 2018) | |

Good explanation @Rakshith. |

Mehr said: (Apr 19, 2019) | |

For rpm; Simply convert this to the minute, we multiply 60 with rps 400*60. |

Shoon said: (Aug 24, 2019) | |

1min = 60sec. If 400rps then 400/60 rpm. As from small quantities to bigger quantities we do division, from bigger quantities to small we do multiplication. Kindly explain it. |

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