- #1
jesuslovesu
- 198
- 0
Homework Statement
Assume that the magnitude of the magnetic field outside a sphere of radius R is B = B0 (R/r)^2. Determine the total energy stored in the magnetic field outside the sphere.
Homework Equations
I think it's necessary to use the energy density equation.
u = B^2/(2*u0)
total energy = u * volume.
The Attempt at a Solution
By just plugging in the given data, I come up with (2*pi*B0^2*R^3)/(u0*3). Assuming that r = R. Or 2*pi*B0^2*R^4/(3r*u0) if I don't assume that. My book's answer is similar except that the 3 in the denom. is not there. So I think I need to use calculus but I don't quite see how to set it up...
Last edited: