Physics 2005

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Physics 2005in 2009
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Auguste Coulomb
Coulombs Torsional Balance
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How did mankind begin to find out about the atom?
BIG SURPRISE FOR RUTHERFORDMOST PARTICLES WENT
STRAIGHT THROUGH THE GOLD FOIL. Explaination m
uch of the atomic volume was now assumed to
contain only the very light electrons, which
could not produce much deflection. Accordingly,
many alpha particles would pass through the atom,
deflected only slightly by the electrons and the
long-range Coulomb interaction with the nucleus
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How did mankind measure charge?
Milliken
first let oil drops fall until they reached
terminal velocity. Measured the terminal
velocity. at terminal velocity the oil drop is
not accelerating. So the total force acting on
it must be zero, gravitydrag0 , This lets us
calculate the mass of each oil drop Finally,
use an electric field to stop the falling then
the force of Gravity is exactly cancelled by the
electric force, which determines The charge. x
Electric force
Oil
Gravity
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Millikens actual drawing, he measured
e1.5924(17) x 10-19 coulombs which is a touch
low, due to an error in the viscosity of air