Calculating time in which flux changes

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Discussion Overview

The discussion revolves around calculating the time it takes for the magnetic flux through a 50-turn coil to change from 10 mWb to 20 mWb, given an induced emf of 62.5V. Participants are exploring the application of Faraday's law of electromagnetic induction in this context, focusing on the correct interpretation of the formula and the units involved.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • Some participants express uncertainty about the correctness of the formula used for calculating time, which is derived from Faraday's law: E = N × (change in flux) / (time).
  • One participant transposes the formula to find time as t = (Number of turns × Change in flux) / E, resulting in a calculation of 8 seconds.
  • Another participant questions whether 8 seconds is a reasonable duration and suggests showing units in the calculations for clarity.
  • One participant proposes an alternative calculation using only the change in flux and emf, yielding a result of 0.16 seconds, although this approach does not account for the number of turns.
  • A later reply points out that the change in flux should be correctly noted as 10 mWb, not 10 Wb, highlighting the importance of unit accuracy in the calculations.

Areas of Agreement / Disagreement

Participants generally agree on the application of Faraday's law but express differing views on the correctness of the calculations and the interpretation of units. The discussion remains unresolved regarding the most accurate method for calculating the time.

Contextual Notes

There are limitations regarding the assumptions made about the units of magnetic flux and the implications of the number of turns in the coil. The participants have not reached a consensus on the correct approach to the problem.

jitznerd
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1. Homework Statement [/b]

If the magnetic flux linking all the turns of a 50 turn coil changes from 10mWb to 20mWb and induces an emf of 62.5V in the coil, calculate the time over which the flux changes.

Homework Equations



e=Nd x change in flux / dt

The Attempt at a Solution



Not sure if this is correct formula but transposed formula to:

t = Number of turns x Change in flux / e

= 50 x 10 / 62.5

t = 8s
 
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jitznerd said:
1. Homework Statement [/b]

If the magnetic flux linking all the turns of a 50 turn coil changes from 10mWb to 20mWb and induces an emf of 62.5V in the coil, calculate the time over which the flux changes.

Homework Equations



e=Nd x change in flux / dt

The Attempt at a Solution



Not sure if this is correct formula but transposed formula to:

t = Number of turns x Change in flux / e

= 50 x 10 / 62.5

t = 8s

Could you do it one more time, this time showing the units? Your answer may be correct (seems kind of long), but it would be much clearer if you showed units (and included exponents with numbers like milliWebers...)
 
Yeah I thought 8 seconds seemed a long time, that's what made me query if I had gone about it right.

The question is typed exactly as I have been given with those units, then I have used what I think is Faradays law:

E (volts) = N (number of turns) x change in flux (Webers) / Time (s)

Then transposed this to:

Time = N (number of turns) x change in flux (Webers)/ E (volts)

This gave me the 50 x 10 / 62.5 = 8 seconds.

I initially went used:

Change in time = change in flux (Webers) / E (volts)
= 10/62.5 = 0.16 secs (this answer seemed a little more realistic although it hadnt brought the 50 turns into the equation.
 
try a change in flux of 10 mWb (0.01 Wb)
 
jitznerd said:
1. Homework Statement [/b]

If the magnetic flux linking all the turns of a 50 turn coil changes from 10mWb to 20mWb and induces an emf of 62.5V in the coil, calculate the time over which the flux changes.

Homework Equations



e=Nd x change in flux / dt

The Attempt at a Solution



Not sure if this is correct formula but transposed formula to:

t = Number of turns x Change in flux / e

= 50 x 10 / 62.5

t = 8s

The change in flux is not 10 Wb. It's 10 mWb.
 

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