A. The definition and characteristics of static electricity
1. Definition
Static electricity that is relatively static charge, is thesurface of the object excess or deficit of electrostatic charge; is the surfaceof the object positive and negative charges occur in the separation of aphysical phenomenon.
2. The basic physical properties of static electricity
① mutual attraction or repulsion.
② there is a potential difference with the earth.
③ will produce discharge current.
3. The characteristics of static electricity
① high potential: equipment or electrostatic potential on the humanbody can reach tens of thousands to hundreds of thousands of volts, often hundredsto thousands of volts when operating = (people usually do not easily feel thestatic electricity below 3kv).
② low power: usually milli Coulomb (mC,10-3C), micro Coulomb level (μC,10-6C).
③Small current: mostly microampere level (μA,10-6A).
④Short action time: microsecond level (μS,10-6S).
⑤ by the environment: especially the impact of humidity, humidity isrising electrostatic accumulation is reduced, static voltage drop.
Second, the causes of static electricity
1. Microscopic reasons (endogenous)
According to the theory of atomic physics, the material is inelectrical equilibrium when electrically neutral. Due to the contact betweenthe atoms of different substances to produce electron gain and loss, so thatthe material out of balance, electrostatic phenomena.
Matter is composed of molecules, which are composed of atoms,which are electrons with a negative charge and protons with a positive charge.Under normal conditions, an atom has the same number of protons and electrons,and the positive and negative balance, so it shows no external charge.
When two different objects come in contact with each other, itmakes one object lose its charge and electrons are transferred to the otherobject, making it positively charged, while the other object that gets someremaining electrons is negatively charged. If in the process of separation, thecharge is difficult to neutralize, the charge will accumulate, so that theobject with static electricity. That is, an object will be separated from otherobjects in contact with electrostatic.
2. Macro reasons (external causes)
① friction between objects to generate heat, stimulate electrontransfer.
② the contact and separation between objects to produce electrontransfer.
③ electromagnetic induction caused by the imbalance of charge on thesurface of the object.
④The combined effect of friction and electromagnetic induction.
Third, the definition of electrostatic charging and the way
1. Definition of electrostatic charging.
Electrostatic charging includes all processes that occur inpositive and negative charges. Such as: through the solid and solid surface,solid and liquid surfaces between the contact, friction, collision, solid orliquid surface rupture and other mechanical effects of positive and negativecharge separation. Also includes the ionization of gases, jets charged as wellas dust, snow and storms charged in the phenomenon.
2. Electrostatic charging mode.
① frictional charging: electron transfer from one object to another(electron gain or loss).
② contact charging: in fact, the charge is transferred. A chargedobject in contact with an uncharged conductor, so that the conductor with thesame electrical properties of the charge process (proportional distribution).
Contact of dissimilar charges, first neutralized and thenequally divided.
Law: Two identical conductors come into contact and share theremaining charge equally.
Induction charging: When a charged body is close to a conductor,the end of the conductor near the charged body has a different charge and theend far away has the same charge, a phenomenon called electrostatic induction.
Law: the near end of the induction of dissimilar charge, thedistant end of the induction of the same charge.
Also include: thermoelectric, piezoelectric, impulse, freezing,electrolysis, temperature difference, etc.
The physical process of electrostatic generation.
Contact, separation and induction → charge transfer →coupled layer formation → charge separation → electrostatic generation
The nature of the initiation of electricity.
No matter what kind of starting way, the essence is to separatethe positive and negative charges, so that the charge transfer, and not tocreate a charge.
3. Factors affecting the material electrostatic.
① material itself electrostatic properties, the microstructure andnature of the material is the main factor in determining the electrostaticcharging sequence, directly affecting the starting sign and the size of thecharge: ①: the internal chemical composition of thematerial, the material is the main factor in determining the electrostaticcharging sequence.
ⅰ: the internal chemical composition of the substance.
ⅱ: the chemical composition of the substance surface (such aspollution, oxidation, adsorption, etc.).
ⅲ：molecular structure, orientation (stretching changes the molecularorientation to make the charged state change), crystallinity.
ⅳ: object shape, size, spatial location (determine the limit value ofthe object charged electricity)
② the closeness of contact, pressure, speed of friction.
Friction, pressure and other factors are not the necessaryconditions for electrostatic charging, simple "contact - separation"will make the object charged, but friction and other factors can enhance thecharging effect.
③ environmental temperature and humidity.
△ environmental temperature and humidity changes, will cause thematerial surface and its surrounding medium conductivity changes, so that thecharge on the object through the surface of the object and the surroundingmedium leakage changes in the degree of speed, affecting the objectelectrostatic charged electricity.
△ environmental humidity RH> 80%, any object with staticelectricity is very small; RH < 30% and the temperature is low, the objectdue to static electricity can be very large; RH> 40%, the amount of staticelectricity dropped sharply; RH> 60%, the amount of static electricity tendsto stabilize.