I have recently watched an NHK TV program entitled something like "The Century of Moving Images", a documentary of the past 100 years or so in which various cultural, political, historical, and technological events were recorded in vast amounts of motion pictures.
One of the stories in the program focused on Wernher von Braun, the German scientist who developed the V1 rocket, the world's first ballistic missile, for the Nazis during WWII, and who later moved to the US to help Americans build and launch their own rockets. He was a Jew, and for that reason had to leave Germany eventualy. He said he worked for the Nazis because it gave him the oppotunities to study and develop rocket science, and he was "willing to sell his soul to the devils" if it helped him make his dream of space travel come true.
Dr. von Braun was the hero of the author of "Rocket Boys", a memoir by Homer Hickam, Jr., that I've just finished. It was the time of Cold War, and the successful launch of the Russian Sputnik was a big news not just for the US military and politicians, but for ordinary US citizens. One of them was the 11 year old Hickam, who would look up in the night sky, see the Sputnik moving "majestically" across the star-studded sky and be awe-struck. He begins to build his own model rockets, by himself at first. Several of his friends join him later, and they work hard for a national science fair.
A story of a boy's passion for rockets, it is also a story of growing-up of the boy in a small coal town somewhere in the US during the 50's and 60's. Hickam was small and nearsighted, and not the muscular, athletic type like his big brother. But he was adamantly true to his inner callings, resisting and fighting his father and his brother for a long time but gradually learning their, and the town's, own sadness and limitations.
I particularly liked the scene where, towards the end of the book, he lets his father, who has long dominated over his son and hated the boy's un-manly activities, push the launch button for a late-version, greatly improved model rocket, with more than a hundred onlookers gathered around. The rocket flies as high as ever, and Hickam, Sr., can't hide his elation, waving his hat, as if he became his younger, teenage self. Then, he sort of like comes to his senses, and looks at his son, mouth open. The son sees in his eyes something ... something he's probably never seen before.
The Japanese astronaut Dr. Takao Doi is introduced as a friend of the author's, and he plays a small but heart-warming role at the end. It was a very good read.
"The central three turns all 'link' four lines of flux: 28 mWb.
The two outer turns link just two lines of flux: 14 mWb." (Magnetism: quantities, units and relationships)
"Faraday’s Law is bilateral – that is, anapplied voltage produces a changing flux,likewise a changing flux induces a voltage acrossa coil linked to that flux such that the inducedvolts per turn equals the rate of flux change."
"The flux density in the core (which links both windings) is determined solely by voltseconds per turn applied to the primary(Faraday’s Law), independent of loadcurrent."
"Thus, this "leakage" flux links the outer winding but not the inner winding." (Magnetic Field Evaluation in Transformers and Inductors By Lloyd H. Dixon)
"A charge moving through a magnetic field experiences （受ける）a force f perpendicular to both the velocity u and flux density B." ("Magnetic Circuits and Transformers", slides)
"A typical attempt at defining inductance is based on the idea that the flux links the current once in a single loop circuit, and that it links the current N times in an N-turn coil." (Electromagnetic Induction, PDF)
