ELECTRICITY 



19S7 



ELECTRICITY 



How Electricity Is Produced. An electric 

 discharge in air, an electric spark, may be pro- 

 duced by an electric machine, an induction 

 coil, or a transformer. In nature such a dis- 

 charge occurs in lightning. An electric current 

 is produced either by an electric battery or a 

 ^ dynamo. These devices do not in reality pro- 

 duce electricity, for the electricity is present all 

 the time. They merely set the electricity in 

 motion, or produce an electrical tension, or 

 force. Electricity in motion possesses energy; 

 hence these devices produce electrical energy. 

 Energy in some other form is always consumed 

 by these electrical devices to make up for the 

 electrical energy which they give out. For 

 example, a dynamo must always be run by 

 some form of mechanical power such as a steam 

 engine; hence a dynamo uses mechanical en- 

 ergy and gives out electrical energy. 



How Electricity Stores Energy. It is com- 

 monly believed that electricity can be stored. 

 This is an error. Though electricity itself can- 

 not be stored, it can be used to store energy 

 and this stored energy can be made to produce 

 an electric current. This is accomplished by 

 means of a storage battery. 



Electricity as a Cause of Death. With the 

 increasing use of electric currents deaths 

 caused by contact with "live wires" have 'be- 

 come increasingly frequent. It is well to know 

 the cause and the means of preventing such 

 accidents. 



The human body to a certain extent is pro- 

 tected from electric shock by its high resist- 

 ance. The resistance of the body is much 

 greater when the skin is dry than when it 

 is moist; therefore, it is safer to handle an 

 electric wire with dry hands than with moist 

 hands. Careful tests have shown that the re- 

 sistance of the body may be as high as 4,000 

 ohms when the skin is perfectly dry, and as 

 low as 500 ohms when the skin is thoroughly 

 moistened. The average resistance of the 

 human body is probably about 1,200 ohms. 



Alternating current is more dangerous than 

 direct current for the reason that the injurious 



effect is due chiefly to the shock caused by the 

 changing of the current. With direct current 

 the shock is felt only at the instant of starting 

 and of stopping the current. See CURRENT, 

 ELECTRIC, subheads Direct Current; Alternating 

 Current. 



The voltage that will destroy life depends on 

 various conditions, but it is fairly well ntlfr 

 lished that no human being can withstand an 

 alternating electromotive force of 1,500 volts 

 of ordinary frequency. Three hundred volte 

 alternating have been known to produce death. 

 It must not be inferred that it is safe to toy 

 with lower voltages than those mentioned. 

 Lower voltages may produce severe burns and 

 other injurious effects. 



The cause of death by electric shock is gen- 

 erally believed by medical authorities to be 

 the action of the current on the heart, produc- 

 ing contraction of the fibers of that organ, re- 

 sulting in stopping the circulation. The nerv- 

 ous system dies as a result of anaemia follow- 

 ing the sudden arrest of the circulation of the 

 blood. Death may also be due to asphyxia if 

 the current passes only through the brain and 

 upper portion of the spinal cord, arresting only 

 the action of the nerve centers which control 

 breathing. Death by electricity is not instan- 

 taneous, but the experience of persons who 

 have been rendered unconscious by electric 

 shock and have recovered indicates that it is 

 not painful. 



Emergency Directions. The treatment in 

 case of severe electric shock consists in keep- 

 ing the body warm by wrapping it in warm 

 blankets or clothing and applying heat by some 

 means, such as hot water bottles to the feet, 

 and using artificial respiration as in a case of 

 drowning. If the patient when found is still 

 touching the wire, it is not safe to touch his 

 body or the wire with the bare hands. He 

 should be pulled away from the wire by the 

 clothing or the wire may be torn from his 

 grasp with a dry stick. With a thick leather 

 glove on the hand it is safe to take hold of the 

 body or the wire, if the glove is dry. E.E.B. 



Uses of Electricity 



Electricity has become our willing and ready 

 servant. Within the last half century the dis- 

 coveries of new powers of this remarkable force 

 and the invention of machines for utilizing 

 these powers have constituted some of the 

 greatest wonders in the world of science. The 

 first important application of electricity to 



practical service was in the operation of the 

 telegraph in 1844 (see TELEGRAPH). The in- 

 vention of other devices was slow until about 

 1880, but since that time these inventions have 

 increased rapidly, both in number and variety. 

 The uses of electricity are so many that it is 

 nearly impossible to enumerate them. So 



