Electromagnetism - Find length of coil

  • Thread starter Deathfish
  • Start date
  • #1
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Homework Statement


Calculate the length l of an an iron-free cylindrical coil if it has 9400 turns (N), a thickness of 0.6cm and an inductance L = 68 mH. Take magnetic field constant [tex]\mu[/tex]o = 4[tex]\pi[/tex] x 10-7 Wb/Am

(a) l = 63mm
(b) l = 54mm
(c) l = 46mm
(d) l = 36mm


Homework Equations



L = N2 [tex]\mu[/tex]o [tex]\mu[/tex]r A / l


The Attempt at a Solution



0.068 = (9400)2 x ( 4[tex]\pi[/tex] x 10-7) [tex]\mu[/tex]r A / l

how to calculate if [tex]\mu[/tex]r and A are not given??
 
Last edited:

Answers and Replies

  • #2
Zryn
Gold Member
310
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Given that the core is iron-free, what sort of material would you expect to find there? This material has a very nice relative permeability for calculations!

If you have a (circular cross section of a) piece of wire that is 0.6cm thick (diameter), what is the (cross sectional) Area of this wire?

*NB: Beware of units, as 'l' is in meters, 'A' is in meters squared and 'L' is in Henry's.
 
Last edited:

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