Physics - Moving charges in magnetic fields
Moving charges in magnetic fields
Whenever a moving positive or negative charge enters a magnetic field, it
will experience a force. That is, the magnetic field exerts a force on the
moving charge. This force only occurs while the charge is in motion. The
optimum force occurs if the charge is moving at right angles to the field
lines. In this case the motion of the charge, the magnetic field lines and
the resultant force are all mutually perpendicular. This would have the
effect of curving the path of the charge as shown below. If a charge enters
a field parallel to the field lines then no force occurs.
View the direction of force video.
The direction of the force exerted on a positive charge can be determined
using the right-hand slap rule. With the right hand held flat, if the
fingers are aligned in the direction of the magnetic field lines and the
thumb points in the direction of motion of a positive charge, then the palm
indicates the direction of the force on the charge. If a negative charge is
involved, just point the thumb in the opposite direction to its motion.
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