Entries by rude man

A Simplified Synthesis of Financial Options Pricing

Financial options (the right to purchase (“call“) or sell (“put“) stock (or other assets)) at a fixed price at a future date have been around for a long time. They are attractive for the option buyer since his/her total risk is the premium (price) paid for the option, as contrasted with futures contracts which are […]

A New Interpretation of Dr. Walter Lewin’s Paradox

Much has lately been said regarding this paradox which first appeared in one of W. Lewin’s MIT lecture series on ##{YouTube}^{(1)}##.  This lecture was recently critiqued by C. Mabilde in a second YouTube video and submitted as a  post in a PF ##{thread}^{(2)}##.  The latter cited a third source, that of K. T. McDonald of […]

Modulation vs. Beating Confusion

A long time ago I read a paper in the IEEEProceedings recounting the history of the superheterodyne receiver. Overall it was a very interesting and informative article, with one exception: in it the author remarked that the modulation (or mixing) principle was really nothing new, being already known to piano tuners who traditionally used a […]

A Brachistochrone Subway Is Not a Cost-effective Idea

It is apparent that a subway tunnel could be built without the need for supplied energy like electricity, assuming zero friction everywhere.  The tunnel would go underground, level off and then climb back up, all just by exchanging potential and kinetic energy. However, the question arises: what should be the shape of the tunnel for […]

Misconceiving Mutual Inductance Coefficients

  A commonly used formula for mutual inductance M between two nearby coils L1 and L2 is M = k√(L1*L2). This formula however assumes equal percentage flux linkages between the two coils. This requirement is often omitted in several of the references I have looked at. That this requirement is not necessarily met can be […]