How to calculate the time over which flux changes

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Homework Help Overview

The discussion revolves around calculating the time over which magnetic flux changes in a coil, specifically a 50 turn coil experiencing a change in magnetic flux from 10 mWB to 20 mWB, resulting in an induced e.m.f. of 62.5 V.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the formula E = -N (change in flux) / (change in time) but expresses confusion regarding the negative sign associated with time, questioning its validity and how to handle it.

Discussion Status

Some participants have provided feedback on the interpretation of the polarity of the e.m.f., noting that the absolute value of the e.m.f. can be considered, which may help clarify the original poster's concerns about negative time.

Contextual Notes

The original poster's calculation resulted in a negative time value, raising questions about the implications of this result and the assumptions made regarding the formula's application.

poortech
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1. if the magnetic flux linking all the turns of a 50 turn coil changes from 10 mWB to 20 mWB and induces an e.m.f. of 62.5 V in the coil, calculate the time over which the flux changes.

i know the formula to calculate the flux which is

E = -N change in flux / change in time.

to calculate the change in time we just need to change E with change in time in the formula, but by doing this answer will be negative which is not possible as time can not be negative. how to get rid of this -ve. or is it ok if i don't use it at all.


my answer is -0.008 Sec.



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The Attempt at a Solution

 
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The 62.5V polarity was not defined with respect to coil geometry so your answer is correct when made positive.
 
62.5 V is an absolute value of e.m.f
 
thnx a lot guyz... :D
 

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