The stability of electron motion in antenna and nuclear electric field is analyzed by considering the mass-velocity formula in this paper. It is pointed out that the essence of antenna radiation is bremsstrahring radiation. If nucleus is stationary or its motion speed is not high, the electron motion around the nucleus is stable and no radiation will be caused. If the nucleus is in thermal motion and electrons are not moving around the nucleus, Bremsstrahlung can be caused. On this basis, this paper gives a strict proof of the Ohm's law in classical electromagnetic theory, reveals the dynamic nature of resistance. A new mechanism of superconductivity is proposed. It is considered that one of the fundamental reasons for superconductivity is that the nucleus stops vibrating at the critical temperature and the electrons move in the conductor without radiation. It is proved that the superconducting energy gap is caused by the decrease of the ground state energy of electrons moving around the nucleus after the nucleus stops vibrating. The conditions under which nuclei stop vibrating on a one-dimensional infinitesimally long lattice are discussed, and a formula for calculating the critical temperature of a superconductor of elemental elements is derived, which is more consistent with the experimental data than the formula of BCS theory. This method can also clarify the superconductivity of conductors, the Meissner effect and other thermodynamic properties, and provide microscopic explanations for the phenomena of multi-energy gap, pseudogap, second-class superconductor, and d wave of high-temperature superconductors, providing new ideas for theoretical and experimental research of high-temperature superconductors, and exerting important influence on solid state physics.