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Energy Stored in Magnetic Field of Solenoid

  • Thread starter x^2
  • Start date
  • #1
x^2
21
1

Homework Statement


The magnetic field inside an air-filled solenoid 39.9cm long and 2.00cm in diameter is 0.800T. Approximately how much energy is stored in this field?


Homework Equations



U=(1/2)LI^2
=> U = (1/2)(B^2)(area*length)/(u)

The Attempt at a Solution


I discovered how to derive the bottom equation from the top equation from http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/indeng.html#c2

The derivation on the site seems to make sense, but when I try to use the bottom equation I get:
U = (1/2)(0.8^2)(Pi*0.01^2)*(0.399)/(8.85*10^-7) = 45.324 J

What am I missing here?

Thanks,
x^2
 

Answers and Replies

  • #2
Kurdt
Staff Emeritus
Science Advisor
Gold Member
4,812
6
Check the value you use for permeability.
 
  • #3
x^2
21
1
Check the value you use for permeability.
Oh wow do I feel stupid now..... Thanks for the help!
x^2
 

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