Why is there a lightning rod on the building?
Because of cosmic rays or other ionization phenomena, the atmosphere will produce positive and negative ions. Positive and negative ions move freely, which makes the air conductive. When the atmospheric potential is not the same, the negative ions move to the positive region, the positive ions move to the negative region, and the positive and negative charges neutralize the electric balance.
Lightning usually occurs between clouds or cloud between the bottom and ground. The only thing to avoid is the thunder and lightning between the clouds and the ground. If the upper part of the cloud of charged, is negatively charged, the ground is induced by the electricity is charged on the ground projection (buildings, trees or body) is likely to occur and the charge discharge phenomenon, by the lightning disaster. But in the clouds, things are different. Clouds are made up of tiny droplets of water that are adsorbed on water droplets and become spherical charges. Because of the quality of water droplets, they are clumsy; even water droplets of only a few microns in diameter are a heavy burden of gas ions. So the charge in the clouds moves slowly, and the electric balance is hard to reach. Under the influence of atmospheric electric field, positive and negative charges accumulate in the upper and lower layers of cloud. Often positive charges are gathered in the upper layer of clouds, and negative charges are gathered in the lower layers of clouds. When the charged cloud is closer to the ground, clouds and ground form a huge capacitor. The cloud and the earth are the poles of a capacitor, and the atmosphere between the clouds and the ground is dielectric. In thunderstorms, the voltage between the poles varies greatly, reaching tens of thousands of volts per hour. When the electric field is stronger than the dielectric strength of the air, it will break the air and discharge it.
The so-called lightning phenomenon, is the accumulation of charge air to a considerable number of clouds, and near the charged clouds or between objects have great potential, the formation of a strong electric field, the two part of the opposite charge of air surrounding the obstacles to break and strong discharge, then send out sound and light on the path via the. Is the lightning.
During discharge, charged particles impact air molecules, causing air molecules to ionize. An electrical path consisting of electrons and ions is formed between the clouds and the earth. The charge in the clouds goes down this path, and this is the lightning we see coming into the ground from the clouds. Due to the instantaneous current of up to tens of thousands or even hundreds of thousands of amperes, lightening the temperature of the surrounding air as tens of thousands of degrees, due to gas heating, air pressure suddenly increased to near dozens and even hundreds of atmospheric pressure, the huge pressure to the surrounding the outbreak, a frightening sound like an explosion, this is the thunder.
