# أوراق عمل Electrostatics الكهرباء الساكنة الفيزياء منهج انجليزي الصف الثاني عشر عام

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أوراق عمل Electrostatics الكهرباء الساكنة الفيزياء منهج انجليزي الصف الثاني عشر عام

. Force : arises between electric charges, magnetic foræ (arises between magnetic poles)

. Weak force: works during the decay of a in which an electron and a neutrino (ß) are automatically emitted from some nuclei

- strong force: located inside the nucleus of the atom

. Gravitational force : (arises between physical objects)

The effects of static emricity are observed in

Electrostatic: The study of electrical charges that are and held somewhere

The effEts of static elEtricity are in

1- Lightning

- Attract hair to the comb when combing on a dry day

- Attract the paper scraps to the plastic ruler when kneading the ruler with a piece Of wool

- Attract adhesive tape when the paste and then remove from the surface Of the table

- repulsion of adhesive when the paste and then from the table surface with another adhesive was pasted and then removed from the table surface as well

#### I .2 Electric Charge

Electric charge: A physical Of a material that only when an electrical equalization occurs

The law of similar charges each other and different charges attract

Charging mechanism: transport of negatively charged particles (elwtrons) from atoms. material and its molecules into atoms of another material

. If the material loses electrons, its charge

. If the material acquires electrons, its charge becomes negative

. The susceptibility of materials to loss or gain of electrons varies depending on how electrons are bound to the nucleus

The unit of electric charge is Coulomb (C) and is in the International System of Units (A.s), 1 s 1 C 1 A

Conservation Law Of Charge : The total amount Of electrical charge in a closed tem does not change (Electric charge can neither created nor destroyed. In closed system

#### 4- Superconductors

Materials resist to conduct electricity zero, no loss of energy occurs

They are effective as superconductors at very low temperatures

Such as niobium and titanium alloy, which is kept at 4.2 K

Over the past 20 years new materials have been developed that act as superconductors at a relatively high temperature of 77.3 K critical degree

So far, superconducting materials at room temperature 300 K have not been detected

#### I .4 Electrostatic Charging

Charging the object with a static charge. The car battery is an energy source where chemical energy is used to separate positive and negative charges

Many insulating rods can be charged with a positive or negative charge from the power source

Grounding : discharging the charge of the charged object via a connection to the ground

The Earth is a nearly infinite reservoir of charge

#### Electrostatics

An electroscope: is a device that gives an observable response when it is charged The electroscope consists of

. Two strips of very thin metal foil, in a tie position connect one of them Hinge at the middle so that it stays away from the other fixed connector when charging

. A ball attached to the top of the electroscope connected to the conductors and allow the entry of charge or they exit easily

Q: Kitchen aluminum foil is not suitable Because it is too thick, but hobby shops sell thinner metal foils Inducing a charge

#### applications  Precipitator

is used to remove ash and other particulates resulting from the burning Of coal to generate electricity

The ESP consists of wires and plates, with the wires held at a high negative voltage relative to a series of plates held at a positive voltage. the exhaust from the coal-burning process enters the ESP from the left. passing near the wires pick up a negative charge

These particles are then attracted to one of the plates and stick there The gas continues through the ESP, leaving the ash and other particulates behind. The accumulated material is then shaken off the plates to a hamper below. This waste can be used for many purposes, including construction materials and fertilizer

Particulate ionized and sticking to plate particulate Gas With particulates Clean gas

FIGURE 21.17 Opration Of an electrostatic precipitator to dean the exhaust gas Of a coal- fired plant. The view is from the top of the device

#### laser Printer

The paper path follows the blue arrows. Paper is taken from the paper tray or fed manually through the alternate paper feed. The paper passes over a drum where the toner is placed on the surface of the and then passes through a fuser that melts the toner and permanently affixes it to the paper The drum is negatively charged with electrons using a wire held at high voltage. Then laser light is directed at the surface Of the drum. Wherever the laser light strikes the surface Of the drum, the surface at that point is discharged. A laser is used because its beam is narrow and remains A line Of the image printed is written one pixel (picture element or dot) at a time using a laser beam directed by a moving mirror and a lens. A typical laser printer can write pixels per inch, with many printers being able to write 6(1) or 1200 pixels

#### Electrostatics

per inch. The surface of the drum then passes by a roller that picks up toner from the toner cartridge. Toner consists of small, black, insulating particles composed of a plastic-like material. The toner roller is charged to the same negative voltage as the drum. Therefore, wherever the surface of the drum has been discharged, electrostatic forces deposit toner on the surface of the drum

Any portion of the drum surface that has not been exposed to the laser will not pick up toner. As the drum rotates, it next comes in contact with the paper. The toner is then transferred from the surfaæ of the drum to the paper. Some printers charge the positively to help attract the charged toner. As the drum rotates, any remaining toner is scraped off and the surface is neutralized with an erase light or a rotating erase drum in preparation for printing the next image. The paper then continues on to the fuser, which melts the toner, producing a permanent image on the paper. Finally the exits the printer