* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ørsted - Piazza
Wireless power transfer wikipedia , lookup
Electromotive force wikipedia , lookup
Hall effect wikipedia , lookup
Magnetic field wikipedia , lookup
Superconducting magnet wikipedia , lookup
Electric machine wikipedia , lookup
Magnetochemistry wikipedia , lookup
Electrostatics wikipedia , lookup
Superconductivity wikipedia , lookup
Force between magnets wikipedia , lookup
Magnetic monopole wikipedia , lookup
Galvanometer wikipedia , lookup
Scanning SQUID microscope wikipedia , lookup
Electrification wikipedia , lookup
Magnetoreception wikipedia , lookup
Magnetohydrodynamics wikipedia , lookup
Electromagnetic radiation wikipedia , lookup
Eddy current wikipedia , lookup
Multiferroics wikipedia , lookup
Computational electromagnetics wikipedia , lookup
James Clerk Maxwell wikipedia , lookup
Electricity wikipedia , lookup
History of electrochemistry wikipedia , lookup
Maxwell's equations wikipedia , lookup
History of electromagnetic theory wikipedia , lookup
Mathematical descriptions of the electromagnetic field wikipedia , lookup
Electromagnetic field wikipedia , lookup
Lorentz force wikipedia , lookup
Ørsted Notice that we are starting to see modern style professors as scientists and researchers. - professor at the University of Copenhagen. On 21 April 1820, during a lecture, Ørsted noticed a compass needle deflected from magnetic north when an electric current from a battery was switched on and off, confirming a direct relationship between electricity and magnetism. [note that light and heat also emanate from electrified wires] Hans Christian Ørsted (1777 – 1851) Danish physicist and chemist. Ampére Ampére felt that if a current in a wire exerted a magnetic force on a compass needle, two such wires also should interact magnetically. In a series of ingenious experiments he showed that this interaction was simple and fundamental - parallel (straight) currents attract, anti-parallel currents repel. The force between two long straight parallel currents was inversely proportional to the distance between them and proportional to the intensity of the current flowing in each. André-Marie Ampère (1775 – 1836) We see people quantifying the behaviour of magnetic and electric interactions. Faraday -- background Michael Faraday (1791 -- 1867) - Faraday was born in Newington Butts. - apprenticed to a bookbinder - In 1812, at the age of twenty, and at the end of his apprenticeship, Faraday attended lectures by the eminent English chemist Humphrey Davy of the Royal Society. - Faraday subsequently sent Davy a three-hundred-page book based on notes that he had taken during these lectures. Davy hired him as a secretary and he eventually rose to take Davy’s position. - Although Faraday received little formal education he was one of the most influential scientists in history. Treated by Davy’s wife as a ser vant. He refused many honours including being buried at Westminster Abbey, a knighthood, and the presidency of the Royal Society. Faraday -- accomplishments Michael Faraday (1791 -- 1867) - discovered two compounds of chlorine and carbon - investigated diffusion of gases - investigated alloys of steel - produced new types of glass for optical purposes - determined that magnets can affect light (rotating their polarisation) - invented a type of Bunsen burner - discovered benzene - liquified chlorine gas - determined the laws of electrolysis Faraday -- accomplishments He did not credit Davy (his boss) with discussions. Michael Faraday (1791 -- 1867) - designed the first electric motor (for which he got in trouble) - discovered electromagnetic induction (a changing magnetic field produces an electric field) - constructed the first dynamo - proposed that electromagnetic fields extend into empty space - discovered diamagnetism - worked on mining safety, corrosion, environmental science, & educational reform. Faraday -- fields "On the physical character of the lines of magnetic force" Phil. Mag. June 1852, pg 407 ff. Michael Faraday (1791 -- 1867) Faraday -- fields "On the physical character of the lines of magnetic force" Phil. Mag. June 1852, pg 407 ff. Michael Faraday (1791 -- 1867) Not sure what a radiation force is ... he seems to distinguish it from electric force. Faraday -- fields Faraday imagined that electric charges created electric fields and magnets created magnetic fields. These fill space, and take time to change. Field lines are defined by the direction in which a positive “test charge” would move. Faraday -- fields Faraday -- fields There is an energy density associated with these fields. 1 2 u= E 2 [Notice that symmetry fixes the shape of the field.] Faraday -- fields scalar fields T (x, y, z, t) P (x, y, z, t) Faraday -- fields vector fields B(x, y, z, t) E(x, y, z, t) v(x, y, z, t) Maxwell -- background - family was comfortable and had connections to the peerage - arrival at private school with homemade shoes and a provincial accent earned him the nickname ‘Daftie’. - published his first scientific paper at age 14 - died of abdominal cancer at age 48 James Clerk Maxwell (1831 – 1879) Scottish physicist. - predicted (correctly) that the rings of Saturn are made up of particles (rather than a solid or a liquid) - also worked on colour theory, control theory, kinetic theory, and thermodynamics [Maxwell is regarded by most modern physicists as the scientist of the 19th century who had the greatest influence on 20th-century physics, and he is ranked with Sir Isaac Newton and Albert Einstein for the fundamental nature of his contributions. In 1931, on the 100th anniversary of Maxwell's birth, Einstein described the change in the conception of reality in physics that resulted from Maxwell's work as 'the most profound and the most fruitful that physics has experienced since the time of Newton.'] Maxwell -- accomplishments James Clerk Maxwell - derived “Maxwell’s equations” that unify all previous work on electricity and magnetism (and unifies those forces as electromagnetism) - from his equations showed that an wave of oscillating electric and magnetic fields exists. Derived that the speed of this wave is 310,740,000 m/s (c=2.99 x108 m/s) (1864) - published A Treatise on Electricity and Magnetism (1873) (1831 – 1879) Scottish physicist. "We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena." -- Maxwell MAXWELL, James Clerk. A Treatise on Electricity and Magnetism. Oxford: Clarendon Press, 1873. Octavo, original russet cloth; largely unopened. Custom cloth box. Two volumes. $10,500. Maxwell -- accomplishments Since all wave known phenomena require a medium to oscillate, Maxwell believed that the propagation of light required a medium for the waves, dubbed the luminiferous aether. One is tempted to identify this with the frame of absolute space. Light [ a changing electric field makes a magnetic field; a changing magnetic field makes an electric field] μ and ε are conversion factors to yield units of energy density. 1 2 uE = E 2 1 B2 uB = 2 µ A = amp = unit of electric current = 6.241×1018 electrons / second. µ0 = 1.26 · 10 0 6 kg m A2 s 2 2 4 A s 12 = 8.85 · 10 kg m3 c= 1 µ c = 2.99 · 108 m/s ✔ Scientific Notation 3.41 · 103 = 3410 3.41 · 106 = 3410000 3.41 · 10 1 = 0.341 3.41 · 10 5 = 0.0000341 Units distance (m) time (s) mass (kg) electric charge (C) temperature (K) luminous intensity (cd) [amount of substance (mol)] Dimensional Analysis circumference = 2 π r area of a circle = π r2 Light Light is a transverse wave. Sound is a longitudinal wave. Ocean waves are both. The Speed of Light “This second inequality appears to be due to light taking some time to reach us from the satellite; light seems to take about ten to eleven minutes [to cross] a distance equal to the half-diameter of the terrestrial orbit.” -Romer Ole Christensen Rømer (1644 – 1710) The orbit of Io about Jupiter is like a clock. As we move away from Io, it will appear to take longer to ‘tic’. Rømer compared the apparent duration of Io's orbits as Earth moved towards Jupiter (F to G) and as Earth moved away from Jupiter (L to K). (1677) The Speed of Light Armand Hippolyte Louis Fizeau (1819 – 1896)) The Spectrum of Light f= c E = hf c = 299, 792, 458m/s h = 6.62606896(33) · 10 34 Q: why are there 7 colors? Js