# Homework Help: Magnetic-field energy question

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1. Mar 30, 2015

### Jack_M

1. The problem statement, all variables and given/known data
What is the magnetic-field energy in a 10.0cm3 volume of space where B = 3.50T?

2. Relevant equations
u = B2/2μ0

3. The attempt at a solution
Using the equation I got an answer of 4.87*105 J/m3 which is incorrect

2. Mar 30, 2015

### phyzguy

It doesn't ask for the energy density, which is what you gave. It asks for the energy, so your final answer should be in Joules, not Joules/m^3.

3. Mar 30, 2015

### Jack_M

Should an answer using that formula along with those units be correct, though? I only have 2 more submissions available.

4. Mar 30, 2015

### phyzguy

Yes, you're on the right track. You have calculated the energy density almost correctly. I got 4.87*106 J/m3, so one of us made a mistake. Then how do you go from energy density to energy?

5. Mar 30, 2015

### Jack_M

Oh I see now. I should multiply by the volume of the space correct?

6. Mar 30, 2015

Yes.