  We study the energy conversion laws of the macroscopic harmonic $LC $
oscillator, the electromagnetic wave (photon) and the hydrogen atom. As our
analysis indicates that the energies of these apparently different systems obey
exactly the same energy conversion law. Based on our results and the
wave-particle duality of electron, we find that the atom in fact is a natural
microscopic $LC$ oscillator. In the framework of classical electromagnetic
field theory we analytically obtain, for the hydrogen atom, the quantized
electron orbit radius. Without the adaptation of any other fundamental
principles of quantum mechanics, we present a reasonable explanation of the
polarization of photon, the Zeeman effect, Selection rules and Pauli exclusion
principle. Particularly, it is found that a pairing Pauli electron can move
closely and steadily in a DNA-like double helical electron orbit. Our results
also reveal an essential connection between electron spin and the intrinsic
helical movement of electron and indicate that the spin itself is the effect of
quantum confinement. In addition, a possible physical mechanism of
superconductivity and the deeper physical understandings of the electron mass,
zero point energy, and the hardness property of electron are also provided.
Finally, we show analytically that the Dirac's quantization of magnetic
monopole is merely a special handed electron at absolute zero-temperature,
which strongly suggests that any efforts to seek for the magneticmonopole in
real space will be entirely in vain. Furthermore, it appears that the
electron's spin and the magnetic monopole are actually two different concepts
for one possible physical phenomenon.
