上海交通大学：《材料与文明》课程教学资源（参考资料）Understanding Mater_Chapter 10

174 10.The Age of Electronic Materials Electrical The first observations involving electrical phenomena in mate- Phenomena rials probably began when static electricity was discovered. (Lightning,of course,preceded these experiments,but this could not be controlled by man.)Around 600 B.C.,Thales of Miletus,a Greek philosopher,realized that a piece of amber,having been rubbed with a piece of cloth,attracted feathers and other light particles.Very appropriately,the word "electricity"was later coined by utilizing the Greek word electron,which means amber. It was apparently not before 2300 years later that man again be- came seriously interested in electrical phenomena.In 1729, Stephen Gray (a British Chemist)found that some substances conducted the "effluvium"of electricity whereas others did not. In 1733,C.F.Du Fay (a French scientist)postulated the existence of two types of electricity,which he termed glass (or vitreous) electricity and amber (or resinous)electricity,depending on which material was rubbed.Benjamin Franklin'later designated to them the plus and the minus sign,implying that one type of electricity would cancel the other.His ideas were based on his famous kite experiments in 1752 in which he demonstrated "the sameness of electrical matter with that of lightning."This clas- sification was expanded almost 100 years later to include five kinds of electricity,namely,frictional,galvanic (animal),voltaic, magnetic (by induction),and thermal. Magnetism Magnetism(or,more precisely,ferro-or ferrimagnetism),that is, the mutual attraction of two pieces of iron or iron ore,was like- wise already known to the antique world.The term "magnetism" is said to have been derived from a region in Turkey (or north- ern Greece?),called Magnesia,which had plenty of iron ore.Now, iron does not immediately attract another piece of iron.For this, at least one of the pieces has to be magnetized,that is,simply said, its internal "elementary magnets"need to be aligned in parallel. Magnetizing causes no problem in modern days.One merely places a piece of iron into a wire coil through which a direct cur- rent is passed for a short time.(This was discovered by the Dan- ish physicist Hans Christian Oersted at the beginning of the 19th century.)But how did the ancients do it?There may have been at least two or three possibilities.First,a bolt of lightning could have caused a magnetic field large enough to magnetize a piece of iron or iron ore.Once one magnet had been produced and iden- tified,more magnets could have been obtained by rubbing virgin pieces of iron with the first magnet.There could have been an- 11706-1790,American publisher,scientist,and diplomat

The first observations involving electrical phenomena in materials probably began when static electricity was discovered. (Lightning, of course, preceded these experiments, but this could not be controlled by man.) Around 600 B.C., Thales of Miletus, a Greek philosopher, realized that a piece of amber, having been rubbed with a piece of cloth, attracted feathers and other light particles. Very appropriately, the word “electricity” was later coined by utilizing the Greek word electron, which means amber. It was apparently not before 2300 years later that man again became seriously interested in electrical phenomena. In 1729, Stephen Gray (a British Chemist) found that some substances conducted the “effluvium” of electricity whereas others did not. In 1733, C.F. Du Fay (a French scientist) postulated the existence of two types of electricity, which he termed glass (or vitreous) electricity and amber (or resinous) electricity, depending on which material was rubbed. Benjamin Franklin1 later designated to them the plus and the minus sign, implying that one type of electricity would cancel the other. His ideas were based on his famous kite experiments in 1752 in which he demonstrated “the sameness of electrical matter with that of lightning.” This classification was expanded almost 100 years later to include five kinds of electricity, namely, frictional, galvanic (animal), voltaic, magnetic (by induction), and thermal. Magnetism (or, more precisely, ferro- or ferrimagnetism), that is, the mutual attraction of two pieces of iron or iron ore, was likewise already known to the antique world. The term “magnetism” is said to have been derived from a region in Turkey (or northern Greece?), called Magnesia, which had plenty of iron ore. Now, iron does not immediately attract another piece of iron. For this, at least one of the pieces has to be magnetized, that is, simply said, its internal “elementary magnets” need to be aligned in parallel. Magnetizing causes no problem in modern days. One merely places a piece of iron into a wire coil through which a direct current is passed for a short time. (This was discovered by the Danish physicist Hans Christian Oersted at the beginning of the 19th century.) But how did the ancients do it? There may have been at least two or three possibilities. First, a bolt of lightning could have caused a magnetic field large enough to magnetize a piece of iron or iron ore. Once one magnet had been produced and identified, more magnets could have been obtained by rubbing virgin pieces of iron with the first magnet. There could have been anElectrical Phenomena Magnetism 174 10 • The Age of Electronic Materials 11706–1790, American publisher, scientist, and diplomat

10.The Age of Electronic Materials 175 FiGURE 10.1.Depiction of an ancient Chinese compass called a sinan. (or Zhe'nan)Zhe point;nan south.The spoon-shaped device was carved out of a lodestone and rested on a polished bronze plate.The rounded bottom swiveled on the "earth plate"until the spoon handle pointed to the south. other possibility.It is known that if a piece of iron is repeatedly hit very hard,its"elementary magnets"will be "shaken loose"and will align in the direction of the earth's magnetic field(which is quite weak,i.e.,only about half a gauss).An iron hammer,for ex- ample,is north magnetic on its face of impact in the northern hemisphere.Could it have been that a piece of iron was used as a hammer and thus became a permanent magnet?A third possi- bility is that iron-or nickel-containing meteorites responded with an alignment of their"elementary magnets"in an electromagnetic field during their immersion into the earth's atmosphere. One of the major applications of magnetism was the compass which is said to have been invented independently in China (be- fore A.D.1100,possibly before 1040)and in Western Europe (about A.D.1187).Other sources emphasize that the Chinese,as early as A.D.80(or even earlier),had a device called a sinan, which consists of a piece of iron ore carved (by a jade cutter) into the shape of a ladle;see Figure 10.1.When placed on a pol- ished plate of bronze,called the "earth plate,"the spoon swiveled until the handle pointed to the south which was considered by the Chinese rulers to be the imperial direction toward which all seats had to face.The ladle resembles the Big Dipper (or great bear)whose pointer stars point to the Polaris or North Star.An- other device,the iron fish compass,described in A.D.1044 in a Chinese book was fabricated by allowing molten iron rods to so- lidify in the north-south direction that is,in the earth magnetic field which induces permanent magnetism in the metal(thermo remanence).The fish-shaped leaf was placed on water where it

other possibility. It is known that if a piece of iron is repeatedly hit very hard, its “elementary magnets” will be “shaken loose” and will align in the direction of the earth’s magnetic field (which is quite weak, i.e., only about half a gauss). An iron hammer, for example, is north magnetic on its face of impact in the northern hemisphere. Could it have been that a piece of iron was used as a hammer and thus became a permanent magnet? A third possibility is that iron- or nickel-containing meteorites responded with an alignment of their “elementary magnets” in an electromagnetic field during their immersion into the earth’s atmosphere. One of the major applications of magnetism was the compass which is said to have been invented independently in China (before A.D. 1100, possibly before 1040) and in Western Europe (about A.D. 1187). Other sources emphasize that the Chinese, as early as A.D. 80 (or even earlier), had a device called a sinan, which consists of a piece of iron ore carved (by a jade cutter) into the shape of a ladle; see Figure 10.1. When placed on a polished plate of bronze, called the “earth plate,” the spoon swiveled until the handle pointed to the south which was considered by the Chinese rulers to be the imperial direction toward which all seats had to face. The ladle resembles the Big Dipper (or great bear) whose pointer stars point to the Polaris or North Star. Another device, the iron fish compass, described in A.D. 1044 in a Chinese book was fabricated by allowing molten iron rods to solidify in the north-south direction that is, in the earth magnetic field which induces permanent magnetism in the metal (thermo remanence). The fish-shaped leaf was placed on water where it FIGURE 10.1. Depiction of an ancient Chinese compass called a sinan. (or Zhe nan) Zhe point; nan south. The spoon-shaped device was carved out of a lodestone and rested on a polished bronze plate. The rounded bottom swiveled on the “earth plate” until the spoon handle pointed to the south. 10 • The Age of Electronic Materials 175

176 10.The Age of Electronic Materials floated on the surface while the fish's head pointed to the south. A Chinese book printed in 1325 describes a wooden turtle,con- taining a loadstone and a needle as its tail,pointing to the south There are no reports that the Chinese used these devices for nav- igation probably because China was a land-based culture.They were probably used instead to align the edges of pyramids,etc., along the north-south axis or as described above. In the western world,on the other hand,the first mention of a compass was by an English Augustian monk(Alexander Neckam, 1157-1217)in his book entitled "De Naturis Rerum."There is also a document by an Arab writer who,in 1242,reports that a mag- netic needle floating on water on top of a wooden splinter points to the north star.The bishop of Acre,Jaques Vitry,wrote in 1218 that the compass is a necessary instrument for navigation on the seas.Around 1300 the south Italian mariners of Amalfi are said to have perfected to some degree the compass from a needle float- ing on water to a round box (called later a "bussola")in which a compass card with a wind rose,divided into 32 points,is attached to the rotating needle.During the 15th century it was realized that the compass needle does not point to true north but assumes an angle,called variation (or declination),with the meridian.Mag- netism is also mentioned in poetic works such as the Divine Com- edy by Dante (written between 1310 and 1314)or in La Bible by the French monk Guyot de Provins (written about 1206).Mag- netism was (and occasionally still is today)considered as a re- pellent against witchcraft and most anything,to heal madness and insomnia,and as an antidote against poison. The modern compass consists quite similarly to the bussola of a pivoted bar magnet whose tip,which points to the general di- rection of geographic north,is called the "north-seeking pole"or simply the north pole.The bowl is suspended in gimbals,that is, in rings,pivoted at right angles to each other so that the com- pass is always level.Around 1500,the term lodestone appears in the literature when referring to magnetized iron ore,that is,iron oxide,particularly when used in a compass.This word is derived from the old English word lode,which means to lead or to guide. Optical The study of optical phenomena likewise goes back to antiquity. Phenomena Interestingly enough,there used to be an intense debate whether in vision something moves from an object to the eye or whether something reaches out from the eye to an object.In other words, the discussions revolved around the question of whether vision is an active or a passive process.Specifically,Pythagoras,a Greek philosopher and mathematician (living during the 6th century

floated on the surface while the fish’s head pointed to the south. A Chinese book printed in 1325 describes a wooden turtle, containing a loadstone and a needle as its tail, pointing to the south. There are no reports that the Chinese used these devices for navigation probably because China was a land-based culture. They were probably used instead to align the edges of pyramids, etc., along the north-south axis or as described above. In the western world, on the other hand, the first mention of a compass was by an English Augustian monk (Alexander Neckam, 1157–1217) in his book entitled “De Naturis Rerum.” There is also a document by an Arab writer who, in 1242, reports that a magnetic needle floating on water on top of a wooden splinter points to the north star. The bishop of Acre, Jaques Vitry, wrote in 1218 that the compass is a necessary instrument for navigation on the seas. Around 1300 the south Italian mariners of Amalfi are said to have perfected to some degree the compass from a needle floating on water to a round box (called later a “bussola”) in which a compass card with a wind rose, divided into 32 points, is attached to the rotating needle. During the 15th century it was realized that the compass needle does not point to true north but assumes an angle, called variation (or declination), with the meridian. Magnetism is also mentioned in poetic works such as the Divine Comedy by Dante (written between 1310 and 1314) or in La Bible by the French monk Guyot de Provins (written about 1206). Magnetism was (and occasionally still is today) considered as a repellent against witchcraft and most anything, to heal madness and insomnia, and as an antidote against poison. The modern compass consists quite similarly to the bussola of a pivoted bar magnet whose tip, which points to the general direction of geographic north, is called the “north-seeking pole” or simply the north pole. The bowl is suspended in gimbals, that is, in rings, pivoted at right angles to each other so that the compass is always level. Around 1500, the term lodestone appears in the literature when referring to magnetized iron ore, that is, iron oxide, particularly when used in a compass. This word is derived from the old English word lode, which means to lead or to guide. The study of optical phenomena likewise goes back to antiquity. Interestingly enough, there used to be an intense debate whether in vision something moves from an object to the eye or whether something reaches out from the eye to an object. In other words, the discussions revolved around the question of whether vision is an active or a passive process. Specifically, Pythagoras, a Greek philosopher and mathematician (living during the 6th century Optical Phenomena 176 10 • The Age of Electronic Materials

10.The Age of Electronic Materials 177 B.c.),believed that light acts like feelers and travels from the eyes to an object and that the sensation of vision occurs when these rays touch that object.Euclid,a Greek mathematician,recognized at about 300 B.C.that light propagates in a straight line.Further, he related that the angle of reflection equals the angle of incidence when light is impinging the surface between two different media. Even though refraction was also known and observed in the an- tique world,it was not before 1821 when W.Snell,a Dutchman, formulated its mathematical relationship.(Refraction is the change in the direction of propagation when light passes the in- terface between two media having different optical densities.) Optical materials,particularly glasses,became of prime im- portance once the refractive power of transparent materials was discovered.This found applications in magnifying glasses and notably in telescopes.Plane and convex mirrors,as well as con- vex and concave lenses,were known to the Greeks and the Chi- nese.Their knowledge probably went back to a common source in Mesopotamia,India,or Egypt.There is written evidence that the telescope was invented independently many times before Galileo built his version in 1609.He observed with it the craters of the moon,the satellites of Jupiter,and the orbiting of Venus around the sun,thus shattering the Ptolemaic theory (A.D.150). As we shall describe in Chapter 15,glass was known to the Egyp- tians as early as 3500 B.C.,and crude lenses have been unearthed in Crete and Asia Minor that are believed to date from 2000 B.C. Modern optical devices include lasers,optical telecommunica- tion,optical data storage (compact disk),and possibly,in the near future,the optical computer. Thermal Heat was considered to be an invisible fluid,called caloric,until Phenomena late into the eighteenth century.It was believed that a hot piece of material contained more caloric than a cold one and that an object would become warmer by transferring caloric into it.In the mid-1800s,Mayer,Helmholtz,and Joule discovered inde- pendently that heat is simply a form of energy.They realized that when two bodies have different temperatures,thermal energy is transferred from the hotter to the colder one when the two are brought into contact. All taken,electrical,magnetic,optical,and thermal phenom- ena were considered to be unrelated to each other until the eigh- teenth century and were thought to be governed by their own in- dependent laws.Many brilliant scientists have corrected this view and enhanced our knowledge on this in the past two centuries. Among them were Oersted,Ampere,Volta,Ohm,Coulomb

B.C.), believed that light acts like feelers and travels from the eyes to an object and that the sensation of vision occurs when these rays touch that object. Euclid, a Greek mathematician, recognized at about 300 B.C. that light propagates in a straight line. Further, he related that the angle of reflection equals the angle of incidence when light is impinging the surface between two different media. Even though refraction was also known and observed in the antique world, it was not before 1821 when W. Snell, a Dutchman, formulated its mathematical relationship. (Refraction is the change in the direction of propagation when light passes the interface between two media having different optical densities.) Optical materials, particularly glasses, became of prime importance once the refractive power of transparent materials was discovered. This found applications in magnifying glasses and notably in telescopes. Plane and convex mirrors, as well as convex and concave lenses, were known to the Greeks and the Chinese. Their knowledge probably went back to a common source in Mesopotamia, India, or Egypt. There is written evidence that the telescope was invented independently many times before Galileo built his version in 1609. He observed with it the craters of the moon, the satellites of Jupiter, and the orbiting of Venus around the sun, thus shattering the Ptolemaic theory ( A.D.150). As we shall describe in Chapter 15, glass was known to the Egyptians as early as 3500 B.C., and crude lenses have been unearthed in Crete and Asia Minor that are believed to date from 2000 B.C. Modern optical devices include lasers, optical telecommunication, optical data storage (compact disk), and possibly, in the near future, the optical computer. Heat was considered to be an invisible fluid, called caloric, until late into the eighteenth century. It was believed that a hot piece of material contained more caloric than a cold one and that an object would become warmer by transferring caloric into it. In the mid-1800s, Mayer, Helmholtz, and Joule discovered independently that heat is simply a form of energy. They realized that when two bodies have different temperatures, thermal energy is transferred from the hotter to the colder one when the two are brought into contact. All taken, electrical, magnetic, optical, and thermal phenomena were considered to be unrelated to each other until the eighteenth century and were thought to be governed by their own independent laws. Many brilliant scientists have corrected this view and enhanced our knowledge on this in the past two centuries. Among them were Oersted, Ampère, Volta, Ohm, Coulomb, 10 • The Age of Electronic Materials 177 Thermal Phenomena

上海交通大学：《材料与文明》课程教学资源（参考资料）Understanding Mater_Chapter 10 - The Age of Electronic Materials