I lately took to writing responses on the Quora Q&A site for recreation.
I rarely stray from electronics and one or two othersubject areas where
I have some insight. But the other day, withinternal alarm bells
ringing, I strayed into a basic physics question,where some
high-schooler (?) transcribed a question directly from somequestion
paper, as they sometimes do.
You will recognize it, I expect. Two spheres of 4 and 6 cm radius are
charged to 80 and 60 uCoulomb respectively. How is the charge
redistributed when the spheres are connected with a wire? I answered on
general principle, in this way: the charge is redistributed in
proportion to the spheres' surface area. 4^2 / (4^2 + 6^2) X (80 + 60)
uC and 6^2 / (4^2 + 6^2 ) X (80 + 60) uC. about 43 : 97 uC I was
surprised to find (when I finally checked) that the charge division (as
given in online sources) is proportional to spheres' radii, not area.
56 : 84 uC How was I so easily falsified? Brian W