Crystal DavidsonMr. Darmand

September 16, 20156A3

September 14, 2015

The Photocopier

Photocopiers consist of a drum or belt covered with a layer of photoconductive material. A photoconductive material conducts electricity when struck by light (photo meaning light and conductive referring to conducting electrons).When a photocopier is started a high voltage wire distributes a positive charge evenly on the surface of the belt or drum. An intense beam of light moves across the sheet of paper to be copied placed on the glass surface. The dark areas on the paper absorb the light and the white areas reflect the light back onto the drum/belt below. The reflected light strikes the positively charged photoconductive material on the metal neutralizing it by producing electrons. The dark areas on the paper like the text or picture that do not reflect the light leave regions of positive charges on the surface of the belt/drum like a shadow. Negatively charged, dry black pigment particles known as toner are then spread over the drum/belt. These negatively charged particles are attracted to the positively charged regions on the drum/belt because opposite charges attract. A blank sheet of paper is passed over the charged wire making it positive and then passed over the drum/belt. The positively charged paper attracts the toner off the drum/belt. The paper plus toner is then heated and passed through rollers to melt and fuse the toner to the paper.

Paint Spraying/Crop Spraying

The principles of electrostatics are used by industry in the process of paint spraying for e.g. the automotive industry when spraying cars. The nozzle of the spray gun is given a charge. The paint droplets exiting the nozzle gain this charge. As the droplets all hold the same charge they repel each other so that they spread out into a fine mist. The object to be painted is grounded or earthed. The charged droplets are attracted to the grounded object, even the back of it due to the electrostatic attraction. That is because charged objects are attracted to uncharged objects. This process requires less paint and gives a uniform finish.

The same principle is used to benefit farmers in crop spraying. If the fertilizer/pesticide is given the same charge the droplets repel to form a larger cloud thereby increasing the coverage. These are then attracted to the uncharged crops.

The Electrostatic dust Precipitator

Electrostatic precipitators are used in industry for environmental protection. In factories, power plants and chemical plants smoke and other exhaust have to be treated to remove dust particles and other particulates before it is released into the atmosphere. Highly positively charged wires are stretched across the centre of the chimney or exhaust vent to form a grid. The wires are charged to a positive charge of about 50,000V. As the smoke passes over the wires the particles carried in the smoke become positively charged. These particles are then attracted towards negatively charged collecting plates where they stick. Thus, the dust particles are separated from the smoke which then carries on up the chimney and into the atmosphere. The negatively charged collecting plates are periodically struck with a mechanical hammer to remove the dust particles which then drop into a collecting bin. The process relies on the principle that opposite charges attract so the charges of the plates can be reversed.

Computer/ Silicon chips

Materials that allow electricity to flow through them quite readily are conductors and those that do not are insulators. Metals make up most of the conductors, while nonmetals such as plastics, wood, and glass are the insulators. However there are certain elements in the middle of the periodic table in groups 14 and 15, that are semiconductors: notably silicon and germanium. Normally insulators, these elements can be made to behave more like conductors if small quantities of impurities are added to them in a process known as doping. If antimony is added to silicon, it would be given slightly more electrons than it would normally have—and also the power to conduct electricity. The result of this is that Silicon becomes progressively more conductive i.e. becomes a semiconductor the more impurity is added. Silicon "doped" this way is called n-type. If boron is added instead of antimony some of silicon's electrons will be removed, leaving behind "holes" that work as "negative electrons," carrying a positive electric current in the opposite way. That kind of silicon is called p-type. Putting areas of n-type and p-type silicon side by side creates junctions where electrons behave in very interesting ways that's how electronic, semiconductor-based components like diodes, transistors, and memories are created.

Why shouldn’t computer chips be touched by the human body

There is a danger of damaging these computer chips with the buildup of static electricity that is held by the human body. They are extremely susceptible to static electricity, which can cause considerable damage if it is zapped with even a small amount. Microchip damage can occur if it is exposed to static electricity as low as 10 volts, and humans are not able to perceive static electricity until it has reached about 1,500 volts. To avoid zapping components with static electricity, precaution should be taken to precautions to ground the static electricity before touching any of the internal components of the computer. Wearing an ESD wrist strap or working on an anti-static mat will prevent any static electricity from damaging the computer. Another way to ground the static electricity is to touch the internal metal frame of the computer's case while the computer is plugged into an electrical socket. The static electricity will be discharged and grounded as the electrical circuit is grounded via the AC outlet.

Air fresheners

Some people purchase what are called air ionizers to freshen and purify the air in their homes. They work on a similar principle as the dust precipitator. These devices strip electrons from smoke molecules, dust particles, and pollen in the air, just as what happens in creating static electricity. These charged dust and smoke particles are then attracted to and stick to a plate on the device with the opposite charge. After a while, much of the pollution is drawn from the air. Since charged particles will also stick to neutral surfaces, some of them can stick to the wall near the ionizer, making it very dirty and difficult to clean.

Defibrillators

A defibrillator is a machine that is used by surgeons or paramedics to restart the heart if it stops. Two paddles with insulated handles are charged from a high voltage supply around 200–1000 volts. This is done to pass an electric current through the heart so it's shocked into functioning normally again. The patient's heart receives roughly 300 joules of electrical energy this is equivalent to about as much as a 100 watt incandescent lamp uses in three seconds. Defibrillators consists of an electric supply unit and two metal electrodes called paddles that are pressed very firmly to the patient's chest using insulating plastic handles (so the person using them doesn't get a shock too). The important thing is getting the current to flow through the heart, so where the paddles are applied is crucial. In order for the electric current to flow properly, and to reduce the risk of skin burns, the electrodes have to be applied close enough together. They must also make good electrical contact with the skin, so a solid or liquid conducting gel is usually applied to the patient's chest first.

Heating effect of   electricity  

Heating effect of electricity is one of the widely used effects in the world. When electric current is passed through a conductor, it generates heat due to the resistance it offers to the current flow. The work done in overcoming the resistance is generated as heat. Applications of the heating effect of electric current include appliances like electric immersion water heater and the electric iron. All of these have a heating element in it. The electric heating is also used to produce light, as in an electric bulb. Here, the filament must retain as much of the heat generated as is possible, so that it gets very hot and emits light.