Definition
Corona discharge
Conductors with pointed ends have very high electric field near these ends which may cause dielectric breakdown in air. The charge may jump from the conductor to the air because of increased conductivity of the air, accompanied by a visible glow near the pointed ends. This phenomena is corona discharge.
Definition
Principle and working of an electrostatic generator
An electrostatic generator is a device which generates high voltages by gradually accumulating a charge through a low-power current, which can then be stored for later use. These devices convert mechanical action into an electric charge, producing what is known as static electricity.
Devices of this type generally fall into two categories: triboelectric or friction machines and electrostatic induction machines.
Friction-type electrostatic generators rely on the triboelectric effect, which is the generation of a small electric current when two materials are rubbed against one another. The first machine had a rotating globe of sulfur that accumulated an electrostatic charge by rubbing one's hand against it as it turned. Later research showed that other materials, like glass, could also be used.
Electrostatic induction machines, also called influence machines, operate on the principle of charge by induction. Through this process, a charged object can impart an opposite charge to another object simply by being placed near the second object. This process is coupled with some type of mechanical operation, like a rotating disk of glass, to continually add charge to the storage object.
Definition
Van de Graff generator
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate electric charge on a hollow metal globe on the top of an insulated column, creating very high electric potentials. It produces very high voltage direct current (DC) electricity at low current levels.
A simple Van de Graaff generator consists of a belt of rubber (or a similar flexible dielectric material) running over two rollers of differing material, one of which is surrounded by a hollow metal sphere. Two electrodes, in the form of comb-shaped rows of sharp metal points, are positioned near the bottom of the lower roller and inside the sphere, over the upper roller. One comb is connected to the sphere, and another comb to ground. The method of charging is based on the triboelectric effect, wherein simple contact of dissimilar materials causes the transfer of some electrons from one material to the other.
A simple Van de Graaff generator consists of a belt of rubber (or a similar flexible dielectric material) running over two rollers of differing material, one of which is surrounded by a hollow metal sphere. Two electrodes, in the form of comb-shaped rows of sharp metal points, are positioned near the bottom of the lower roller and inside the sphere, over the upper roller. One comb is connected to the sphere, and another comb to ground. The method of charging is based on the triboelectric effect, wherein simple contact of dissimilar materials causes the transfer of some electrons from one material to the other.
Law
Uses of Van de Graff generator
The Van de Graff generator was developed as a particle accelerator in physics research, its high potential is used to accelerate subatomic particles to high speeds in an evacuated tube. It was the most powerful type of accelerator in the 1930s until the cyclotron was developed. Today it is still used as an accelerator to generate energetic particle and x-ray beams in fields such as nuclear medicine.
 |
| BookMarks |
Page 11 Page 12 Page 13 Page 14 Page 15
0 Comments
Post a Comment