Download 2.1.7 particle movement in magnetic fields

The
effect of an electric field on
the motion of a charged particle
can be to change speed or
direction.
The effect of a magnetic field
on a charged particle can only
be to change its direction.
This is because the force applied
is always perpendicular to its
motion.
 Use
Flemings left to verify the direction of
the force acting on the positive charge.
 In
which direction was this proton introduced
into this field?
 The
force due to the magnetic field causes
centripetal acceleration.
 Therefore –
F
= BQv = mv2/r
r
= mv/BQ
r
is the radius of the circular path (m).
 The
use of both fields in conjunction with
each other is seen in a ‘velocity selector’.
 For
any charged
particle, these fields will
influence their motion.
 If the particles continue
in a straight line then
BQv = QE
 Faster particles will have
a greater force upwards
and slower particles will
move down.