All practical electromechanical energy conversion devices make use of the magnetic field rather than the electric field as the coupling medium. This is because ________

• A. electric field systems present insulation difficulties
• B. electric field systems have more dielectric loss than the magnetic loss, for the same power rating of the machine
• C. in electric field systems, for normal electric field strength, the stored energy density is high
• D. in magnetic field systems, for normal magnetic flux density, the stored energy density is high