Millikan Oil Drop Question
American physicist
Robert Millikan won the
1923 Nobel Prize in
physics. conducted a
series of experiments
that measured the
electrical charge carried
by an electron.
Problem
Two large parallel metal plates are
separated by a distance of 2.0 x 10-3
meters.
The plates are attached to a 4.0 x 103 volt
source.
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Calculate
The FIELD INTENSITY between the
plates ( E = V/d)
Determine the FORCE on an electron in
the FIELD ( F = q E)
Calculate the WORK necessary to move
an electron from the positive plate to the
negative plate in ELECTRON VOLTS and
in Joules ( W = q V)
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Sample Solutions
Field intensity
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Two large parallel metal plates are
separated by a distance of 2.0 x 10-3 m.
The plates are attached to a 4.0 x 10 3 V
E=V/d
= (4.0 x 10 3 V) / ( 2.0 x 10-3 m)
= 2.0 x 10 6 V/m
Force Example
Calculate the force exerted on an electron
on an electric field, whose intensity is
2.0 x 10 –19 C
F =qE
= ( 1.6 x 10 –19 C ) (2.0 x 10 3 N/C)
= 3.2 x 10 –16 N
Work Example
Calculate the work necessary to move an
electron from the positive plate to the
negative plate in eV and in J.
W = qV
= 1 electron x (4.0 x 10 3 V)
= 4.0 x 10 3 eV
Since : 1 eV = 1.6 x 10 –19 J
W = 1 electron x (4.0 x 10 3 V)
= (1.6 x 10 –19 J/ev)(4.0 x 10 3 eV)
= 6.4 x 10 –16 J
Summary
Robert Millikan conducted a
series of experiments that
measured the electrical
charge carried by an electron.
Using the potential ( volts )
formulas based on an
electron „s “pressure”
Solve for FIELD
INTENSITY, FORCE, and
WORK on the electron.