Magnetic flux through a solenoid

Click For Summary

Discussion Overview

The discussion revolves around the calculation of magnetic flux through a solenoid, including the definitions and formulas involved. Participants explore the relationship between the number of turns, the length of the solenoid, and the magnetic flux, as well as the interpretation of magnetic flux itself.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant proposes that the magnetic flux through a single ring is given by the formula πR²nμI, questioning why the total flux for the solenoid is calculated as nL times this flux.
  • Another participant challenges the initial formulas, suggesting that the flux should decrease with the length of the coil and points out an undefined variable in the first formula.
  • A participant expresses confusion about the application of Faraday's law, questioning the necessity of including the length factor L when calculating induced EMF for the entire solenoid.
  • Another participant asserts that there is no length factor L in Faraday's law, supporting the previous claim about the formula's correctness.
  • A later reply acknowledges a misunderstanding regarding the variable n, clarifying that n represents the number of turns per unit length, and thus the total number of turns N is obtained by multiplying n with L.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the correct application of formulas for magnetic flux and induced EMF in a solenoid. There is no consensus on the initial formulas presented, and confusion remains about the definitions and relationships involved.

Contextual Notes

Participants highlight potential misunderstandings regarding the definitions of variables and the relationships between them, particularly concerning the distinction between turns per unit length and total turns in the context of magnetic flux calculations.

quietrain
Messages
648
Reaction score
2
ok, the magnetic field through a single ring is n\muI ,
so the flux is BAcos(theta), with cos(theta)=1, flux = BA = piR2n\muI

so why for the entire solenoid flux, it is now nL*the flux above? where L = length of solenoid

shouldn't multiplying it with just n = number of rings be suffice?

also, i don't really understand the magnetic flux. is it define to be the number of field lines per unit area? it is something like density right? so shouldn't it be flux = B/A ? i am getting confused :X

thanks
 
Physics news on Phys.org
Those formulas look pretty wrong. The flux should decrease with the length of the coil. And your first formula contains a number n that is not even defined for a single loop (or simply n=1)

Maybe this helps: http://en.wikipedia.org/wiki/Solenoid
 
yup, for a single coil , n = 1.

but i don't understand why for the entire solenoid, we use n*L*dflux/dt = induced EMF

shouldn't just multiplying with n be enough? because n = number of turns. and dflux/dt is for 1 turn. so the entire solenoid just needs to be multiplied by n turns. why do we multiply another length L factor? it is taken from masterphysics.com
 
oh i realize where it all went wrong. after reading the question again for the 3000 time, i realize that n was the number of turns per unit length. so to get N, number of turns, we have to multiply n with L. -.-

sorry for the commotion
 

Similar threads

Undergrad Motional EMF in Faraday disc, co-rotating magnet axial mean flux
  • · Replies 5 ·
Replies
5
Views
975
Graduate Magnetic Flux outside of a long solenoid
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Magnetic Flux - Misleading Definition or what?
  • · Replies 24 ·
Replies
24
Views
2K
Undergrad Total magnetic flux of a solenoid
  • · Replies 1 ·
Replies
1
Views
3K
Insights How to Model a Magnet Falling Through a Solenoid
  • · Replies 10 ·
Replies
10
Views
3K
Undergrad How induction works within a coil (nuances of it)
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Induced current in a coil from a constant uniform magnetic field?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Why does the magnetic flux in a solenoid depend on the number of loops?
  • · Replies 2 ·
Replies
2
Views
6K
Undergrad Mutual inductance in a transformer
  • · Replies 16 ·
Replies
16
Views
5K
Undergrad Derivation of the magnetic flux in coaxial cable
  • · Replies 26 ·
Replies
26
Views
4K