Question

11) On a clear day at a certain location, a 96 V / m vertical electric field exists near theEarth's surface. At the same place, the Earth's magnetic field has a magnitude of 6.20 X10^-5 T. Compute the energy densities of the two fields.
u_E = ___________ nJ/m³
u_B= ___________ µJ/m³

Answer 1

the energy density :
electric field :
U(E) = (1/2)ε_o E^2 = (1/2)*8.85x10^-12*96^2 = 40.78 nJ/m³

magnetic field :
U(B) = (1/2)*B^2/μ_o = (1/2)*(6.2x10^-50^2/(4πx10^-7) = 1529.5 μJ/m³