Rectangular coil rotating in magnetic field

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Homework Help Overview

The discussion revolves around a problem involving a rectangular coil rotating in a magnetic field, specifically focusing on the calculation of the rms voltage generated by the coil. The problem includes parameters such as the number of turns, area, rotation speed, and magnetic field strength.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the need to convert the rotation speed from rpm to rad/s to ensure proper unit consistency in the calculations. There is also a focus on the formula E(max)=NBAw and the requirement for all parameters to be in SI units.

Discussion Status

Some participants have provided guidance on unit conversion and the importance of using SI units, while others express confusion regarding the necessity of these conversions. The discussion is exploring different interpretations of the problem setup and calculations without reaching a consensus on the final answer.

Contextual Notes

There is an indication that the original poster's calculations may not align with expected results, prompting questions about unit conversions and the application of formulas. The discussion highlights potential misunderstandings regarding the relationship between different units in the context of the problem.

ihateblackbox
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Homework Statement



A rectangular coil of 80 turns has an area of 0.01m^2. It rotates @ 3000rpm about one of its in plane axes, in a uniform magnetic field having B=1.5T. Calculate the rms voltage generated.

Homework Equations



1 Tesla= 1 Weber/m^2.
Change in flux of 1 Weber per second = 1 Volt induced.

The Attempt at a Solution



(80*0.01*3000*1.5)/60 = change in flux of 60 Wb/s. ==> 60V. 60/[2sqrt(2)]=15sqrt(2)Vrms.

This is not the right answer. The answer is 267Vrms.
 
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3000 rpm, you need to convert that to rad/s. You didn't multiply by π.
 
rock.freak667 said:
3000 rpm, you need to convert that to rad/s. You didn't multiply by π.

I get the right answer then, but don't understand why you would do that?
 
In the formula E(max)=NBAw, B,A and w need to be in SI units (or at least derived SI units) for the units to produce the Volt on the left hand side.

So rpm would need to be converted to radians per second.
 
rock.freak667 said:
In the formula E(max)=NBAw, B,A and w need to be in SI units (or at least derived SI units) for the units to produce the Volt on the left hand side.

So rpm would need to be converted to radians per second.

OK. Many thanks.
 

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