Chapter 24- Magnetism
- magnetic force: (1) Between magnets, it is the attraction of unlike magnetic
poles for each other and the repulsion between like magnetic poles. (2)
Between a magnetic field and a moving charged particle, it is a deflecting
force due to the motion of the particle: The deflecting force is perpendicular
to the velocity of the particle and perpendicular to the magnetic field lines.
This force is greatest when the charged particle moves perpendicular to the
field lines and is smallest (zero) when it moves parallel to the field lines.
- Checkpoint 1: Do both electrical forces and magnetic forces depend on
o Only the magnetic force requires motion.
- The forces that magnets exert on one another are similar to electrical forces
because both can attract and repel without touching, depending on which
ends of the magnets are held near one another.
- One end, called north-seeking pole, points northward, ad the opposite end,
called the south-seeking pole, points southward.
- When the north pole of one magnet is brought near the north pole of another
magnet, they repel.
- Like poles repel each other; opposite poles attract.
- Whereas electric charges can be isolated, magnetic poles cannot.
- Checkpoint 2: Do every magnet necessarily have a north and a south pole?
o Yes, magnets have more than one pair of poles, but, nevertheless,
poles always occur in pairs.
- magnetic fields: the region of magnetic influence around a magnetic pole or a
moving charged particle.
- The direction of the field outside a magnet is form the north pole to the south
o Where the lines are closer together, the field is stronger.
- This magnetic field is due to the “distortions” in the electric field caused by
- A magnetic field is produced by the motion of electric charge.
- If the motion of electric charges produces magnetism, where is this motion in
a common bar magnet?
o In the electrons of the atoms that make up the magnet.
- Figure 24.3: When the compass needle is not aligned with the magnetic field,
the oppositely directed forces in the needle produce a pair of torques (called
a couple) that twist the needle into alignment.
- Two kinds of electron motion contribute to magnetism: electron revolution
and electron spin.
- A pair of electrons spinning in the same direction make up a stronger
Magnetic Domains - magnetic domains: clustered regions of aligned magnetic atoms. When these