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Exploring Electrical Technology

Exploring Electrical Technology. Origins of Electricity & Magnetism (E & M). Origins of E & M. Before the time of Christ: those who became familiar with the mysterious repulsive and attractive forces of certain materials included

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Exploring Electrical Technology

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  1. Exploring Electrical Technology Origins of Electricity & Magnetism (E & M)

  2. Origins of E & M • Before the time of Christ: those who became familiar with the mysterious repulsive and attractive forces of certain materials included • Lodestone: also known as magnetite, is a magnetic oxide of a common metal that has magnetic properties See also: http://www.phy6.org/earthmag/lodeston.htm

  3. Origins of E & M: Chinese • Chinese: probably 1st to use lodestone for navigation • According to Timetables of Science • Chinese Book of the devil valley master contains first known reference to lodestone’s alignment with Earth’s magnetic field; here the lodestone is called a “south-pointer” (310-301 BC)

  4. Origins of E & M:Chinese • According to Timetables of Science • In China, by 271 AD, the first form of a compass was probably used for finding south • Tseng Kung Liang’s Wu Ching tsung yao (a compendium of important military techniques) describes the magnetized iron “fish” that floats in water and can be used for finding south; about the same time Chinese began applying the compass for navigation, most likely using the iron “fish” (1084 AD)

  5. Origins of E & M:Definition of some key terms • Magnetic field: invisible lines of force along which a magnetized needle aligns itself if allowed to move freely • Navigation: finding out how to go (plotting a course) to get where one is going (destination) • Compass: in the magnetic version, relies on a pivoted, magnetized needle and Earth’s magnetic field to provide a reference direction for navigation

  6. Origins of E & M:Chinese • Timetables of Science also cites • Chinese scientist Shen Kuo’s Dream Pool essays that contain the first known reference to the use of a magnetic compass for navigation • Chu Yu’s Pingchow table talk that contains the first mention in Chinese literature of a compass used for seagoing navigation • What about the geography of China might have made Chinese especially interested in the southerly direction?

  7. Origins of E & M:Chinese precede Europeans; Greeks amused • This brief history suggests that Chinese discovered and may have invented the magnetic compass before Europeans. • On the other hand, Greeks intermittently intrigued themselves by mysterious powers of “magical” materials, during early days

  8. Origins of E & M: Greeks • Ancient Greeks noticed both • Static (electric) forces • Magnetic forces • Found lodestone • Mentioned in Greek texts by 800 BC • Claim two possible origins of the word “magnet” • The province of Magnesia where mined (Lucretius) • The shepherd Magnes, its discoverer (Pliny the Elder)

  9. Origins of E & M: Greeks • By around 600 BC, engaging interest emerged among Greeks w/Thales of Miletus • Greek mathematician, astron. & philosopher • Gave an interpretation of matter (~ 575 BC): “water is the basis of all things” • Intrigued by 2 mysterious phenomenon • That magnetite attracts iron • That rubbed amber attracts a light dry object Consider the demonstration as an illustration.

  10. Origins of E & M: Greeks • Greeks were on the trail, but not scientifically yet, nor for applications • Rather they remained a bit confused, amused and entertained at best

  11. Origins of E & M: Compass • Probably 1st practical application of magnet • Apparently 1st invented by Chinese • Origin uncertain: China, Italy or Arabia • 1st known Western reference to magnetic compass (~1195 AD) • By Alexander Neckham (b. St. Albans, England 1157) • In De naturis rerum (on natural things)

  12. Origins: Early Understanding of Magnetism • Promoted by PetrusPeregrinus de Mericourt • Background and occupation: • Published Epistola de magnete • Concepts he contributed • The identity of magnetic poles… • That magnetic poles remain distinct… • The observation that unlike poles… • That a strong magnet can _____ the polarity of a weak one (try on a nail and sense with a compass)

  13. Origins: Early Understanding of Magnetism • Christopher Columbus: discovered declination • By 1550, Robert Norman (English) had described the magnetic dip (inclination):

  14. Summary • Magnetism and Electricity originally discovered as ________ phenomena with special powers • Lodestone became the basis of a magnetic compass to facilitate _________ • Peregrinus promoted understanding of _________ • Experienced navigators discovered two non-ideal aspects of compass performance:

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