Electrostatical Charging

        The electric field on the conductor defines the effect of static.

    Examples

        The electric field from A insulator makes the electrons of B conductor move towards the surface of A looking at B. These electrons make up the bound induced charge.Unless B isn?t in the electric field from A, the movement of charges doesn?t occur. The free induced charge (positive) creates an electric field outside of B, with the field lines eventually terminating on some grounded object. If this field is integrated from B to a ground point, we will get a positive figure, which, by definition, is the voltage of B. Thus we have an uncharged conductor with a positive voltage.

Figure 1. Insulated conductor in the field from a charged insulator

        The condition in Figure 2?de is same as im Figure 1 .But the conductor is grounded.Thus, the voltage of B is zero.But, B has negative charge at the bound. If the ground connection is broken, and B is moved away from the neighborhood of A (in an insulated way), B will still have its negative charge, giving B a negative voltage.Consequently, B is charged by induction.

Figure 2. Grounded conductor in the field from a charged insulator

       In figure 3 an operator holding a positively charged insulative material is standing on an insulating floor. The charge from the material will bind a negative charge on the operator by induction. A positive charge of the same numerical magnitude as the negative charge will cause the operator to have a positive voltage. The field lines from the operator's positive charge will run through the floor covering to the grounded underlayer.

Figure 3. Insulated operator handling a charged piece of insulative material

       In figure 4 there is a hazardous induction event. Operatör is pouring powder from a plastic bag into a tank containing explosive vapors. At the beginnig the operator who is not grounded ,has no charge.But the plastic bag gives him some charge and generate a positive voltage. If operator accidentally touches the tank, a spark discharge occurs, resulting in an explosion that hurts the operator badly.

Figure 4. Ungrounded operator handling insulative materials in an unsafe environment

Charging of Gases

      The kinetic energy that might be imparted to a gas molecule in an airflow even at high velocities is much lower than the thermal kinetic energies at normal temperatures. It is also much lower than the level required to knock an electron off either the gas molecule itself or the container walls

Charging of Powders

      Dust and powders can get charged by contact or friction between the particles, especially if the individual particles have different properties, such as varying sizes or differing materials. Such charging could result in the particles sticking together. More common, however, are processes in which a powder is being transported through a system of tubes, and the powder as a whole is being charged by friction with the walls of the tube system. This kind of charging might take place if either the powder, the tubes, or both are insulative.

Generation Of Static Electric

 An electric effect can be seen only when electrons are removed from some of the atoms in one material and transferred to atoms in another (or maybe even the same) material. Theelectric effect is caused by the attraction between opposite charges and the repulsion between like charges.

         The number of electrons transferred in any charging process is enormous. Here are some examples. If a powder, such as sugar or flour, slides down a tube and sticks to the wall, the charge on each tiny particle could be 10?14 to 10?13 C, i.e., 100,000 to 1 million electrons have been transferred per particle. A person who has walked across a carpeted floor receives a shock when touching a doorknob that typically has a charge of about 10?7 C. Powder sliding down a tube often has a specific charge of about 10?7 C•kg?1. A plastic folder rubbed with a piece of cloth or fur typically produces a charge of 10?7 C per sheet.