1 Problem Conversions of D and H between SI and Gaussian Units

The electric displacement field D has dimensions charge/area and the magnetic field strength H has dimensions current/length. In the SI system the units of D are C(oulomb)/m 2 and the units of H are A/m, while in the Gaussian (cgs) system the units of D are sC(statcoulomb)/cm 2 and the units of H are Oe (oersteds) where 1,2,3 1Oe=ccgs sA(statampere)/cm ( = 1 abampere/cm in the EMU system), (1) and c is the speed of light in vacuum. The conversions of coulombs to statcoulombs, of amperes to statamperes, are that [1, 10, 11] 1C = ccgs 10 sC ≈ 3 × 109 sC, and 1 A = ccgs 10 sA ≈ 3 × 109 sA. (2) The conversion of D is that [10, 11] DSI =1C/m 2 = Dcgs =4πccgs × 10 −5 sC/cm 2 ≈ 12π × 10 5 sC/cm 2, (3) and the conversion of H is that [1, 10, 11] HSI =1A/m =Hcgs =4π × 10 −3 Oe = 4πccgs × 10 −3 sA/cm ≈ 12π × 10 7 sA/cm. (4) However, from eq. (2) we find the conversion