CHAPTER 20 



SHIPBOARD ELECTRICAL SYSTEMS 



Shipboard electrical systems include a great 

 variety of equipment which provides numerous 

 services indispensable to the operation of a 

 modern naval ship. These systems distribute 

 power throughout the ship for offensive and de- 

 fensive weapons, the ship's movement, and ship- 

 board habitability. Since the systems and equip- 

 ment utilizing electric power are often under 

 the cognizance of a division other than the 

 electrical division, a joint responsibility fre- 

 quently exists for the operation, maintenance, 

 and repair of electrical systems and equipment. 



This chapter provides some information on 

 basic electrical theory and gives a brief de- 

 scription of shipboard electrical systems and 

 equipment. 



BASIC ELECTRICAL THEORY 



The word electric is derived from the Greek 

 word meaning amber. The ancient Greeks used 

 the word to describe the strong forces of attrac- 

 tion and repulsion that were exhibited by amber 

 after it had been rubbed with a cloth. Since 

 scientists are still unable to define electricity 

 clearly, and since many of the phenomena which 

 occur cannot be completely explained, theories 

 can only be postulated from the reactions ob- 

 served. 



Through research and experiment, scientists 

 have observed and described many predictable 

 characteristics of electricity and have postulated 

 certain rules which are often called "laws." 

 These laws of electricity, together with the 

 electron theory, are the basis for our present 

 concepts of electricity. 



ELECTRON THEORY 



Every atom is primarily an electrical sys- 

 tem with high speed planetary electrons orbiting 

 around its nucleus. The electron, whose negative 

 charge forms a natural unit of electricity, is 



bound to the atom by the positive charge within 

 the nucleus. 



The electrons in the outer orbits of certain 

 elements are easily separated from the positive 

 nuclei of their parent atoms. Should an outside 

 force be applied, one of these loosely bound 

 electrons will be released from the parent 

 atom, thus becoming a free electron, and travel 

 to another atom. It is on this ability of an elec- 

 tron to move about from one atom to another 

 that the electron theory is based. 



Elements such as silver, copper, gold, and 

 aluminum have many loosely bound electrons 

 and are considered to be good conductors of 

 electricity. In materials used as insulators, 

 electron flow from one atom to another is 

 relatively non-existent, since the planetary elec- 

 trons in the outer orbital shells are more tightly 

 bound to their parent nuclei. 



Ordinarily an atom is most likely to be in 

 that state in which the internal energy is at a 

 minimum, having a neutral electrical charge. 

 However, if an atom absorbs sufficient energy 

 from am. outside source, loosely bound electrons 

 in the outer orbital shells will leave the atom. 

 An atom that has lost or gained one or more 

 electrons is said to be ionized . If an atom loses 

 electrons it becomes positively charged and is 

 referred to as a positive ion ; if an atom gains 

 electrons it is referred to as a negative ion and 

 is said to have a negative charge. Apositive ion 

 will attract any free electron in its surround- 

 ings in order to reach a neutral state. 



STATIC ELECTRICITY 



When two bodies have unlike charges, one 

 positive and the other negative, an electrical 

 force is exerted between the two. This force is 

 called a static charge or an electrostatic force . 



A static charge can easily be produced by 

 the force of friction when two materials are 



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