Why would a lightning-struck tree glow after being hit?
It is not on fire and does not give off heat, but glows.
It was a dark and stormy night. Chris emails he
was walking in the woods "a little after a thunderstorm" when he
noticed the tree. The tree, shattered by an earlier lightning
stroke, stabbed the night like a broken pike. An eerie glow extended ...
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Why charge accumulates, and the field is strongest, on pointed ends of
conductors
An electric field tends to distribute like charges evenly over the surface of
an object, because like charges repel each other. So charges move apart.
The ones inside the object move to the surface, since that way they can get as
far away from each other as possible. Charges on a sphere end up
distributed evenly over the sphere' s surface.
 The
like charges on the line are not in a stable position. The electric field
resulting from their charges will force them to move. Drawing courtesy of
physicist Hannah Sevian, Boston University
You might think like charges on a line would also distribute themselves
evenly over the line. But that doesn't work. Take a look at the
charge second from left end. It wants to get away from the end guy but it
wants even more to get away from the five charges to the right of it. So
the field forces the charge to move a little to its left. The charges end
up distributed the way the lower drawing depicts — crowded towards each end.
The accumulation of charge on the ends makes the field stronger there because the
strength of a field is directly related to the amount of charge. The
greater the charge, the greater the field.
The like charges on the line are in a stable position. Drawing courtesy of
physicist Hannah Sevian, Boston University
Further Reading
Electric Field, by Hannah Sevian, Notes, Boston University, 1999
(Answered Aug. 10, 2009)
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