Calculating Magnetic Energy in Our Classroom

[tomfrank]

Homework Statement

Considering the Earth magnetic field, I need to find the magnetic energy stored in our classroom.

Homework Equations

U= (1/2*\mu) B²

The Attempt at a Solution

Any suggestions?

 

[kuruman]

Your expression is the energy density (Joules/m³). How many cubic meters is the volume of your classroom?

 

[tomfrank]

around 300 cubic meters

 

[ideasrule]

Do you still need help? You can find the value of B online, so you can find the energy density using your formula.

 

[tomfrank]

so once I have B i just put in the equation and solve for U

and then I multiply U by the volume of the classroom?


where do I found accurate value of the magnetic field of the Earth online?

 

[kuruman]

Go to

http://www.ngdc.noaa.gov/geomag/magfield.shtml

 

[tomfrank]

U= (1/8*pi*10^-7 ) *(54,191.9 nT )^2 = 0.001168500483 (J/m^3)

now

U*Volume= Energy classroom = 0.00117 (J/m^3)* 300 = .35 Joule

is this right?

 

[kuruman]

I didn't put in the numbers, but it looks right.

 

[tomfrank]

thank you