Answer:
W = 2.5*10⁻⁴ J (by me)
Explanation:
μy = 5.0 x 10⁻⁴ A·m²
By = 0.5 T
∅ = 0º
If
μx = 5.0*10⁻⁴ A·m²
By = 0.5 T
∅ = 90º
We get ΔU as follows
ΔU = Uf - Ui
Ui = - μy*By*Cos ∅ = - 5.0*10⁻⁴ A·m²*0.5 T*Cos 0º = - 2.5*10⁻⁴ J
Uf = - μx*By*Cos ∅ = - 5.0*10⁻⁴ A·m²*0.5 T*Cos 90º = 0 J
Finally we use the equation
W = - ΔU = - (0 - (- 2.5*10⁻⁴)) J = - 2.5*10⁻⁴ J (by the field)
W = 2.5*10⁻⁴ J (by me)