1. Exploring Electrical Technology Mid 19 th Century Developments in the “Age of Electricity”

2. Preoccupying Questions  If lightning occupied minds of electrical explorers during the 18 th century, one issue that still puzzled the new mid 19 th century explorers was how em waves compare to light.  Success with electric telegraph may well have stirred such a search.

3. On the trail  Kirchhoff Credited with electric circuit laws that complemented Ohm’s Law (V=IR)Credited with electric circuit laws that complemented Ohm’s Law (V=IR)  Current law based on conservation of charge  Voltage law based on conservation of energy In 1857 demonstrated that electric disturbances propagate on highly conductive wireIn 1857 demonstrated that electric disturbances propagate on highly conductive wire All the current that goes into a node must come out. All the voltage drops around a loop equal zero. commons.wikimedia.org/wiki/File:Gustav_Robert...

4. On the trail  James Clerk Maxwell Brilliant theoristBrilliant theorist Developed a coherent treatmentDeveloped a coherent treatment Drew together the work of othersDrew together the work of others  Faraday:  Gauss:  Ampere:  Maxwell’s own contribution: blogphysica.wordpress.com/.../

5. Maxwell’s Written Contribution  2 Publications A Dynamical Theory of the EM Field (1864)A Dynamical Theory of the EM Field (1864) Electricity & Magnetism (1873)Electricity & Magnetism (1873) science.hq.nasa.gov/kids/imagers/ems/waves2.html

6. Maxwell’s Unique Contribution  Predicted changes (time variation) in Electric fields will produce Magnetic fields even w/out electric currents A time varying magnetic field generates an electric field (from Faraday’s Law) Either an electric current or a time varying electric field generates a magnetic field An electric field eminates from electric charge density at a point A magnetic monopole cannot be isolated like an electric charge; magnetic field lines circulate

7. Assessing Maxwell’s Contribution  Classic equations  Survived 20 th century revolutions  Good to 10 -10 cm  Provides powerful symbolic description

8. Reaction to Maxwell’s Theory  Elegant, but not accepted right away  Heinrich Hertz (1886)  If Maxwell illustrated magnificence in mathematical formulation, then Edison showed perseverance of trial and error method led to successful invention; by 1886 Edison was already 39 years old! www.nrao.edu/whatisra/hist_prehist.shtml

9. Thomas (Alva) Edison  From early years, Edison showed his traits  Childhood (born in 1847) Biographical notes from Experiencing Electricity & Electronics, by Hazen, 1993.

10. Edison’s School Experience  At age 7  Behavior punished by schoolmaster  Parents pulled him from public school  Collected almost 100 chemicals commons.wikimedia.org/wiki/File:Young_Thomas_...

11. Edison as a Youth  At age 12, prepared for economic world  Started printing and publishing  Set up his own chemistry lab  Accidentally set baggage car on fire

12. Edison’s Later Life  He became almost completely deaf  From his own perspective, Edison considered his disability a blessing  More next time