Exploring Electrical Exploring Electrical TechnologyTechnology

Origins of Electricity & Origins of Electricity & MagnetismMagnetism

(E & M)(E & M)

Origins of E & MOrigins of E & M

►Before the time of Christ:Before the time of Christ:those who became familiar with the those who became familiar with the

mysterious repulsive and attractive mysterious repulsive and attractive forces of certain materials included forces of certain materials included

►LodestoneLodestone: also known as magnetite, : also known as magnetite, is a magnetic oxide of a common is a magnetic oxide of a common metal that has magnetic propertiesmetal that has magnetic properties

See also: http://www.phy6.org/earthmag/lodeston.htm

Origins of E & M: Origins of E & M: ChineseChinese

►Chinese: probably 1Chinese: probably 1stst to use to use

lodestone for navigationlodestone for navigation►According to According to Timetables of ScienceTimetables of Science

Chinese Chinese Book of the devil valley masterBook of the devil valley master contains first known reference to contains first known reference to lodestone’slodestone’s alignment with Earth’s alignment with Earth’s magnetic fieldmagnetic field; here the lodestone is ; here the lodestone is called a “south-pointer” called a “south-pointer” (310-301 BC)(310-301 BC)

Origins of E & M:Origins of E & M:ChineseChinese

►According to According to Timetables of ScienceTimetables of Science In China, by 271 AD, the first form of a In China, by 271 AD, the first form of a

compasscompass was probably used for finding was probably used for finding southsouth

Tseng Kung Liang’s Tseng Kung Liang’s Wu Ching tsung yaoWu Ching tsung yao (a (a compendium of important military compendium of important military techniques) describes the magnetized iron techniques) describes the magnetized iron “fish” that floats in water and can be used for “fish” that floats in water and can be used for finding south; about the same time Chinese finding south; about the same time Chinese began applying the compass for began applying the compass for navigationnavigation, , most likely using the iron “fish” (1084 AD)most likely using the iron “fish” (1084 AD)

Origins of E & M:Origins of E & M:Definition of some key termsDefinition of some key terms

►Magnetic fieldMagnetic field: invisible lines of force : invisible lines of force along which a magnetized needle aligns along which a magnetized needle aligns itself if allowed to move freelyitself if allowed to move freely

►NavigationNavigation: finding out how to go (plotting : finding out how to go (plotting a course) to get where one is going a course) to get where one is going (destination)(destination)

► CompassCompass: in the magnetic version, relies on : in the magnetic version, relies on a pivoted, magnetized needle and Earth’s a pivoted, magnetized needle and Earth’s magnetic field to provide a reference magnetic field to provide a reference direction for navigationdirection for navigation

Origins of E & M:Origins of E & M:ChineseChinese

►Timetables of Science also citesTimetables of Science also cites Chinese scientist Shen Kuo’s Chinese scientist Shen Kuo’s Dream PoolDream Pool

essays that contain the first known essays that contain the first known reference to the use of a reference to the use of a magnetic magnetic compasscompass for for navigationnavigation

Chu Yu’s Chu Yu’s Pingchow table talkPingchow table talk that contains that contains the first mention in Chinese literature of a the first mention in Chinese literature of a compass compass used for used for seagoing navigationseagoing navigation

►What about the geography of China What about the geography of China might have made Chinese especially might have made Chinese especially interested in the southerly direction? interested in the southerly direction?

Origins of E & M:Origins of E & M:Chinese precede Europeans; Greeks Chinese precede Europeans; Greeks

amusedamused►This brief history suggests that Chinese This brief history suggests that Chinese

discovered and may have invented the discovered and may have invented the magnetic compass before Europeans. magnetic compass before Europeans.

►On the other hand, Greeks On the other hand, Greeks intermittently intrigued themselves by intermittently intrigued themselves by mysterious powers of “magical” mysterious powers of “magical” materials, during early days materials, during early days

Origins of E & M: GreeksOrigins of E & M: Greeks

►Ancient Greeks noticed bothAncient Greeks noticed both Static (electric) forcesStatic (electric) forces Magnetic forcesMagnetic forces

►Found lodestoneFound lodestone Mentioned in Greek texts by 800 BCMentioned in Greek texts by 800 BC Claim two possible origins of the word Claim two possible origins of the word

“magnet”“magnet”►The province of Magnesia where mined (Lucretius)The province of Magnesia where mined (Lucretius)►The shepherd Magnes, its discoverer (Pliny the The shepherd Magnes, its discoverer (Pliny the

Elder)Elder)

Origins of E & M: GreeksOrigins of E & M: Greeks

►By around 600 BC, engaging interest By around 600 BC, engaging interest emerged among Greeks w/Thales of emerged among Greeks w/Thales of MiletusMiletus Greek mathematician, astron. & philosopherGreek mathematician, astron. & philosopher Gave an interpretation of matter (~ 575 BC):Gave an interpretation of matter (~ 575 BC):

““water is the basis of all things”water is the basis of all things”

Intrigued by 2 mysterious phenomenonIntrigued by 2 mysterious phenomenon►That magnetite attracts ironThat magnetite attracts iron►That rubbed That rubbed amberamber attracts a light dry object attracts a light dry object

Consider the demonstration as an illustration.

Origins of E & M: GreeksOrigins of E & M: Greeks

►Greeks were on the trail, but not Greeks were on the trail, but not scientifically yet, nor for applicationsscientifically yet, nor for applications

►Rather they remained a bit confused, Rather they remained a bit confused, amused and entertained at bestamused and entertained at best

Origins of E & M: CompassOrigins of E & M: Compass

►Probably 1Probably 1stst practical application of practical application of magnetmagnet

►Apparently 1Apparently 1stst invented by Chinese invented by Chinese►Origin uncertain: China, Italy or ArabiaOrigin uncertain: China, Italy or Arabia►11stst known Western reference to known Western reference to

magnetic compass (~1195 AD)magnetic compass (~1195 AD) By Alexander Neckham By Alexander Neckham (b. St. Albans, England (b. St. Albans, England

1157)1157)

In In De naturis rerumDe naturis rerum (on natural things) (on natural things)

Origins: Origins: Early Understanding of Early Understanding of

MagnetismMagnetism►Promoted by Petrus Peregrinus de Promoted by Petrus Peregrinus de

MericourtMericourt Background and occupation:Background and occupation: Published Published Epistola de magneteEpistola de magnete Concepts he contributedConcepts he contributed

►The identity of magnetic The identity of magnetic polespoles……►That magnetic poles remain That magnetic poles remain distinctdistinct……►The observation that The observation that unlikeunlike poles… poles…►That a strong magnet can _____ the polarity of a That a strong magnet can _____ the polarity of a

weak one (try on a nail and sense with a weak one (try on a nail and sense with a compass)compass)

Origins: Origins: Early Understanding of Early Understanding of

MagnetismMagnetism►Christopher Columbus: Christopher Columbus:

discovered discovered declinationdeclination

►By 1550, Robert Norman (English) had By 1550, Robert Norman (English) had described the magnetic dip described the magnetic dip ((inclinationinclination):):

SummarySummary

►Magnetism and Electricity originally Magnetism and Electricity originally discovered as ________ phenomena with discovered as ________ phenomena with special powersspecial powers

► Lodestone became the basis of a magnetic Lodestone became the basis of a magnetic compass to facilitate _________compass to facilitate _________

► Peregrinus promoted understanding of Peregrinus promoted understanding of __________________

► Experienced navigators discovered two non-Experienced navigators discovered two non-ideal aspects of compass performance:ideal aspects of compass performance: