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Lecture 25AC Power, Current Wars,The Thing, The Theremin

Friday, November 15, 13

Damped Oscillations: RLC circuits

Energy gradually dumped into

resistor: i^2*R


Alternating Current


Alternating Current

For Example: in USA, V=120 V AC, 60 Hz

But Why Bother?


2 reasons: Transformers and Power loss:

P=i^2RMaintain low current and high voltage for

transmission


Current Wars

vs

Edison Westinghouse/Tesla

DC AC


Edison's publicity campaign (from Wikipedia)

Edison carried out a campaign to discourage the use of alternating current, including spreading disinformation on fatal AC accidents, publicly killing animals, and lobbying against the use of AC in state

legislatures. Edison directed his technicians, primarily Arthur Kennelly and Harold P. Brown, to preside over several AC-driven executions of animals, primarily stray cats and dogs but also unwanted cattle

and horses. Acting on these directives, they were to demonstrate to the press that alternating current was more dangerous than Edison's system of direct current. He also tried to popularize the term for being electrocuted as being "Westinghoused". Years after DC had lost the "war of the currents," in 1902, his film crew made a movie of the electrocution with high voltage AC, supervised by Edison

employees, of Topsy, a Coney Island circus elephant who had recently killed a man.

Edison opposed capital punishment, but his desire to disparage the system of alternating current led to the invention of the electric chair. Harold P. Brown, who was at this time being secretly paid by Edison,

constructed the first electric chair for the state of New York in order to promote the idea that alternating current was deadlier than DC.

When the chair was first used, on August 6, 1890, the technicians on hand misjudged the voltage needed to kill the condemned prisoner, William Kemmler. The first jolt of electricity was not enough to kill Kemmler, and only left him badly injured. The procedure had to be repeated and a reporter on hand

described it as "an awful spectacle, far worse than hanging." George Westinghouse commented: "They would have done better using an axe."


Tesla on the other hand....

“We are like tenant farmers chopping down the fence around our house for fuel when we should be using

Natures inexhaustible sources of energy — sun, wind and tide. ..

Radio, AC Power, florescence, ignition

systems......


Tesla on the other hand....

“There is no thing endowed with life—from man, who is enslaving the elements, to the nimblest creature—in all this world that does not sway in its turn. Whenever action is born from force, though it be infinitesimal, the cosmic balance is upset and the universal motion results.”

Radio, AC Power, florescence, ignition

systems......


Phasor Notation:

• http://www.animations.physics.unsw.edu.au/jw/AC.html

• http://science.sbcc.edu/physics/flash/optics/phasors4.swf


http://www.animations.physics.unsw.edu.au/jw/AC.htmlhttp://www.animations.physics.unsw.edu.au/jw/AC.htmlhttp://www.animations.physics.unsw.edu.au/jw/AC.htmlhttp://www.animations.physics.unsw.edu.au/jw/AC.htmlhttp://science.sbcc.edu/physics/flash/optics/phasors4.swfhttp://science.sbcc.edu/physics/flash/optics/phasors4.swfhttp://science.sbcc.edu/physics/flash/optics/phasors4.swfhttp://science.sbcc.edu/physics/flash/optics/phasors4.swf

Diode

Current is allowed in one direction, but not the other


Use Diodes to build “rectifiers”

Half wave:


Full Wave:


DC is then smoothed with “filters”

High pass filter


DC is then smoothed with “filters”

Low pass filter


Leon Theremin (1896-1993)

• Theremin – the classic Theremin (1920)• Burglar alarm, or "Signalling Apparatus" which

used the Theremin effect (1920s)• Electromechanical television – Nipkow disk

with mirrors instead of slots (ca. 1925)• Terpsitone – platform that converts dance

movements into tones (1932)• Theremin cello – an electronic cello with no

strings and no bow, using a plastic fingerboard, a handle for volume and two knobs for sound shaping (ca. 1930)[32][33][34][35]

• Keyboard theremin (ca. 1930), looking like a small piano, "with hornlike tones"[36]

• Rhythmicon – world's first drum machine (1931)

• The Buran eavesdropping device (1947 or earlier)

• The Great Seal bug, also known as "The Thing" – one of the first passive covert listening devices; first used by the USSR for spying (1945 or earlier)

Soviet Inventor/ KGB Espionage Engineer


http://en.wikipedia.org/wiki/Burglar_alarmhttp://en.wikipedia.org/wiki/Burglar_alarmhttp://en.wikipedia.org/wiki/Mechanical_televisionhttp://en.wikipedia.org/wiki/Mechanical_televisionhttp://en.wikipedia.org/wiki/Nipkow_diskhttp://en.wikipedia.org/wiki/Nipkow_diskhttp://en.wikipedia.org/wiki/Terpsitonehttp://en.wikipedia.org/wiki/Terpsitonehttp://en.wikipedia.org/wiki/Cellohttp://en.wikipedia.org/wiki/Cellohttp://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-32http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-32http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-33http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-33http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-34http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-34http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-35http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-35http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-36http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-36http://en.wikipedia.org/wiki/Rhythmiconhttp://en.wikipedia.org/wiki/Rhythmiconhttp://en.wikipedia.org/wiki/Drum_machinehttp://en.wikipedia.org/wiki/Drum_machine

“The Thing” or “Great Seal Bug”

Theremins device was implanted inside a carved

wooden plaque of the US seal given to ambassador to Soviets as a gesture of friendship. Was

discovered by British radio operator and reverse

engineered by MI5. Later was presented at special UN

meeting in response to the downing of the U2 spy plane


Forced Oscillations in 3 Easy Pieces

• Resistive Load• Capacitive Load• Inductive Load


•Phase angle (ϕ) = 0•Current and Voltage are in phase

Alternating CurrentPurely Resistive Load:


•Phase angle (ϕ) =-90•Voltage “lags” current

Alternating CurrentPurely Capacitive Load:


•Phase angle (ϕ) =+90•Voltage “leads” current

Alternating CurrentPurely Inductive Load:


Type Resistance Phase of (i) V relation

R

C

L

R

X = 1/ωC

LX = ωL

C

0

leads v by 90

lags v by 90

0

0

V=IR

V=IX

V=IX

C

L


Leon Theremin (1896-1993)

• Theremin – the classic Theremin (1920)• Burglar alarm, or "Signalling Apparatus" which

used the Theremin effect (1920s)• Electromechanical television – Nipkow disk

with mirrors instead of slots (ca. 1925)• Terpsitone – platform that converts dance

movements into tones (1932)• Theremin cello – an electronic cello with no

strings and no bow, using a plastic fingerboard, a handle for volume and two knobs for sound shaping (ca. 1930)[32][33][34][35]

• Keyboard theremin (ca. 1930), looking like a small piano, "with hornlike tones"[36]

• Rhythmicon – world's first drum machine (1931)

• The Buran eavesdropping device (1947 or earlier)

• The Great Seal bug, also known as "The Thing" – one of the first passive covert listening devices; first used by the USSR for spying (1945 or earlier)

Soviet Inventor/ KGB Espionage Engineer


http://en.wikipedia.org/wiki/Burglar_alarmhttp://en.wikipedia.org/wiki/Burglar_alarmhttp://en.wikipedia.org/wiki/Mechanical_televisionhttp://en.wikipedia.org/wiki/Mechanical_televisionhttp://en.wikipedia.org/wiki/Nipkow_diskhttp://en.wikipedia.org/wiki/Nipkow_diskhttp://en.wikipedia.org/wiki/Terpsitonehttp://en.wikipedia.org/wiki/Terpsitonehttp://en.wikipedia.org/wiki/Cellohttp://en.wikipedia.org/wiki/Cellohttp://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-32http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-32http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-33http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-33http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-34http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-34http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-35http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-35http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-36http://en.wikipedia.org/wiki/L%C3%A9on_Theremin#cite_note-36http://en.wikipedia.org/wiki/Rhythmiconhttp://en.wikipedia.org/wiki/Rhythmiconhttp://en.wikipedia.org/wiki/Drum_machinehttp://en.wikipedia.org/wiki/Drum_machine

“The Thing” or “Great Seal Bug”

Theremins device was implanted inside a carved

wooden plaque of the US seal given to ambassador to Soviets as a gesture of friendship. Was

discovered by British radio operator and reverse

engineered by MI5. Later was presented as special UN

meeting in response to the downing of the U2 spy plane


Meissner Effect


Pulsars-Highly magnetized

remnant of supernova explosion

-B-field inclined with respect to angular

motion

As star rotates, B field sweeps radiation past our line of sight->

lighthouse effectFriday, November 15, 13

Jocelyn Bell-Discovery:1967

Dubbed: LGM-1


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