Download 3 Simultaneous Magnetic and Electric Fields

Charged Particles Moving in
Simultaneous Electric and Magnetic
Fields
Mrs. Coyle
AP Physics C
Charged Particles Moving in
Electric and Magnetic Fields
• Net force is the sum of the electric and
magnetic force
F = qE + qv x B
Velocity Selector: an instrument that
allows particles of a certain speed to
move through.
• It contains a uniform
electric field that is
perpendicular to a
uniform magnetic field.
Velocity Selector
When net force=0
F = qE + qv x B =0
qE = qv x B
v=E/B
An entering particle of this
speed will continue moving
straight across the plates.
If the particle has a different
speed, then the magnetic
force will be different and the
net force will not be zero.
Mass Spectrometer
m rBo B

q
E
Thomson’s Experiment found
the ratio of charge to mass of
the electron
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