What is pressure? how to produce electioncity by more way.?

 Whenever you speak into a telephone, or other type of microphone, the pressure waves of the sound energy move a diaphragm.  In some cases, wi the diaphragm moves a coil of wire past a magnet, generating electrical energy which is transmitted through wires to a receiver.  Microphones used with public address systems and radio transmitters sometimes operate on this principle.  Other microphones, however, convert the pressure waves of sound directly into electricity.  Crystals of certain materials will develop electrical charges if a pressure is exerted on them.  Quartz, tourmaline, and Rochelle salts are materials which illustrate the principle of pressure as a source of electricity.  If a crystal made of these materials is placed between two metal plates and a pressure is exerted on the plates, an electric charge will be developed.  The size of the charge produced between the plates will depend on the amount of pressure exerted. 

 

ELECTRIC CHARGES FROM PRESSURE + Metal Crystal Plates Meter The crystal can be used to convert electrical energy to mechanical energy by placing a charge on the plates, since the crystal will expand or contract depending on the amount and type of the charge.  Dry Cell PRESSURE FROM ELECTRIC CHARGES Metal Plates While the actual use of pressure as a source of electricity is limited to very low power applications, you will find it in many different kinds of equipment.  Crystal microphones, crystal headphones, phonograph.  Pickups and sonar equipment use crystals to generate electric charges from pressure.

Another method of obtaining electricity is to convert heat into electricity directly, by heating a junction of two dissimilar metals.  For example, if an iron wire and a copper wire are twisted together to form a junction, and the junction is heated, an electric charge will result.  The amount of charge produced depends on the difference in temperature between the junction and the opposite ends of the two wires.  A greater temperature difference results in a greater charge.  A junction of this type is called a thermo-couple and will produce elec-tricity as long as heat is applied.  While twisted wires may form a thermo-couple, more efficient thermo-couples are constructed of two pieces of dissimilar metal riveted or welded together.  Thermo-couple METER SHOWS A READING Thermo-couples do not furnish a large amount of charge and cannot be used to obtain electric power.  They are normally used in connection with heat indicating devices to operate a meter directly marked in de- grees of temperature.

 

 

Electricity may be produced by using light as the source of energy converted to electricity.  When light strikes certain materials, they may conduct electric charges easier, develop an electric charge, emit free electrons or convert light to heat.  The most useful of these effects is the development of an electric charge by a photo cell when light strikes the photo-sensitive material in the cell.  A photo cell is a metallic "sandwich" or disc composed of three layers of material.  One outside layer is made of iron.  The other outside layer is a film of translucent or semitransparent material which permits light to pass through.  The center layer of material is composed of selenium alloy.  The two outside layers act like electrodes.  When light is focused on the selenium alloy through the translucent material an electric charge is de-veloped between the two outside layers.  If a meter is attached across these layers the amount of charge can be measured.  A direct use of this type of cell is the common light meter as used in photography for deter-mining the amount of light which is present.

 

 

The photo electric cell, commonly called an "electric eye" or a "PE Cell," operates on the principle of the photo cell.  The photo electric cell, how-ever, depends upon a battery or some other source of electrical pressure in its operation of detecting changes in light.  The photo cell has many uses, some of which are automatic headlight dimmers on automobiles, motion picture machines, automatic door openers and drinking fountains.

 

 

So far, you have discovered what electricity is and several sources of energy which may be used to produce it.  Another source of electricity commonly used is the chemical action housed in electric cells and batteries.  Batteries are usually used for emergency and portable electric power.

 

Whenever you use a flashlight emergency lantern or portable equipment, Batteries are the main source of power for you will be using batteries.  present-day submarines.  In addition, there is a wide variety of equipment which uses cells or batteries either as normal or emergency power.  "Dead" batteries are a common type of equipment failure and such failures can be very serious.  Cells and batteries require more care and maintenance than most of the equipment on which you will work.  Even though you may use only a few cells or batteries, if you find out how they work, where they are used and how to properly care for them, you will save time and in many cases a lot of hard work.  Now you will find out how chemical action produces electricity and the proper use and care of the cells and batteries that house this chemi- cal action.