Under atmospheric pressure, the ions that make up the plasma hardly obey electromagnetic pressure due to collisions with neutral particles, but electrons freeze in electromagnetic pressure, so the plasma flow is the propagation of electron. When plasma is irradiated onto a spherical or plate-shaped metal object, electrons become charged onto the object's surface, and then the electrons are dispersed into the atmosphere due to repulsion. In a plate-like structure, the charging of angular shapes concentrates the electric field, and electron emission occurs from these angular shapes depending on the intensity of the applied voltage used for plasma generation. A certain quantity of electromagnetic pressure is required for electrons to be released into the atmosphere from the angular section. Therefore, the quantity of electrons generated increases in proportion to the applied voltage, but when the applied voltage is low, electron emission due to the angular shape decreases, so the quantity of retentional electrons on the metal surface increases because the quantity of electrons generated far exceeds the quantity of electrons emitted. Consequently, when the applied voltage is lower, the quantity of electrons charged on the metal surface increases, so the applied voltage and the quantity of charged electrons are inversely proportional, and a negative permittivity is nominally occurred.