Calculating the RMS Value of Sinewave Voltage

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Homework Help Overview

The discussion revolves around calculating the RMS (Root Mean Square) value of a sinewave voltage in the context of a generator's back emf. The original poster expresses difficulty in arriving at the correct answer for a problem involving a generator with specific parameters.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the transition from maximum values to RMS values, with one questioning how to incorporate RMS speed into the calculations. There is also a clarification about the definitions of RMS, peak, and peak-to-peak values in relation to sinewave voltages.

Discussion Status

The conversation is ongoing, with participants exploring the relationship between maximum and RMS values. Some guidance has been provided regarding the definitions of different voltage specifications, but there is no explicit consensus on the approach to solving the problem.

Contextual Notes

Participants are navigating the definitions and calculations related to RMS values, with some confusion about the terminology used, such as "RMS speed." The original poster's problem statement includes specific parameters that may influence the calculations but are not fully explored in the discussion.

Vladi

Homework Statement


I keep telling myself that this problem should be easy, but I keep getting the wrong answer. Any help is appreciated.
A generator has an armature with 500 turns, which cut a flux of 8.00 mWb during each rotation. Compute the back emf it develops when it runs as a motor at 1500 rpm.

Homework Equations


emf= 2pi*(N)(A)(B)(f)*cos(2pi)
Flux=B*A

The Attempt at a Solution


This is the best I could come up with.
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You have found the maximum value. Try finding the rms value.
 
kuruman said:
You have found the maximum value. Try finding the rms value.

If the rms speed is calculated with the following equation: Vrms=Vmax/sqrt(2), does that mean I must plug in the rms speed within the equation? I will give it a shot. Also, how do you know I should be calculating for the rms value? Thank your for your time. I meant to say rms frequency.
 
Last edited by a moderator:
Vladi said:

If the rms speed is calculated with the following equation: Vrms=Vmax/sqrt(2), does that mean I must plug in the rms speed within the equation? I will give it a shot. Also, how do you know I should be calculating for the rms value? Thank your for your time. I meant to say rms frequency.

No, there is no such thing as RMS speed. A sinewave voltage can be specified by its peak value, its peak-to-peak value, or its RMS value. Does one of these agree with the textbook answer?
 

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