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(c) Pause the simulation and use the horizontal ruler to measure the wavelength

ID: 2219461 • Letter: #

Question


(c) Pause the simulation and use the horizontal ruler to measure the wavelength of the

waves. Note that it is more precise to make crossing to crossing" measurements

rather than peak to peak" measurements since it is easier to tell exactly where a

crossing of the axis occurs.

(d) Let the simulation run and then pause it when the driver is at a maximum (i.e. its

highest point). Set the horizontal ruler with the zero end at a crossing. Now run

the simulation for one full oscillation (use the step" button to make sure that you

advance it by a full oscillation). How far has the crossing that you set the ruler's

origin at traveled during one full oscillation of the driver? What general principle




HERE THE LINK


http://phet.colorado.edu/en/simulation/wave-on-a-string








Explanation / Answer

I believe that it was well known that it does not matter whether you move a coil toward a magnet or a magnet toward a coil, in either case an EMF around the coil will occur. But, it was puzzling because in the first case the electrons in the wire are moving through a magnetic field and therefore experiencing a force which propelled them around the coil and, if the coil was open, caused a voltage across the ends; in the second case, there was no apparent law of physics which said that if the field moves and the charges stand still the charges will experience the same force as if it wer them which were moving. Relativity takes care of this because there is no preferred frame of reference and the two should be identical.