Chapter 24: Magnetism Flashcards
The force between any two charged particles depends on the magnitude of the charge on each and their distance of
Separation as specified in Coulomb’s law
When charged particles are moving with respect to each other, the electrical force between electrically charged particles depends also, in a complicated way, on their
Motion
There is a force due to the motion of the charged particles that we call the
Magnetic force
Force of attraction or repulsion between a pair of magnets depends on
Which end of the magnet is held near the other
Magnetic poles behavior similar to
Electrical forces
Strength of interaction depends on the distance between the
Two magnets
Given rise to magnetic force of the two types interacting with each other:
1) North pole
2) South pole
North and South pole
North seeking pole and south seeking pole
Rule for magnetic forces between magnetic poles like
Poles repels and opposite poles area attract
In all magnets cannot have
One pole without the other
No single pole known to
Exist
Simple bar magnet
Poles at the two ends
Horseshoe magnet
Bent U Shape poles at ends
If we continue to split the magnet, we will eventually get down to an iron atom with
A north pole and south pole and these cannot be separated
A weak and strong magnet repel each other. The greater repelling force is by the
Stronger and weaker magnet
Region of magnetic influence surrounding
Magnetic poles and shape revealed by lines that spread from one pole to the other then by convention direction is from the north pole to the south pole
Strength indicated by closeness of the lines
1) Line close together (denser); strong magnetic field
2) Lines farther apart (less dense); weak magnetic field
Magnetic field produced by two kinds of electron motion
1) Electron pin
2) Electron revolutions
Electron spin main contributor to
Magnetism and pair of electrons spinning in same direction creates a stronger magnet and pair of electron spinning in opposite direction cancels magnetic field the other
Electron revolution orbits or energy levels that electrons occupy
Around the nucleus of an atom
Magnetized clusters of
Aligned magnetic atoms
Permanent magnets made by placing pieces of iron or similar magnetic materials in
A strong magnetic field
Stroking material with a magnet to
Align the domains
Permanent magnet can be naturally occuring (lodestone) or created by
1) Alignment of domains by an external field
2) Domain remain once external magnetic field is removed
Temporary magnet alignment of domains return to
Random arrangement once external magnetic field is removed
When a magnet is broken into two pieces, each piece is
An equally strong magnet
Since a moving charge produces a magnetic field, it follows that a
Current of charges also produces a magnetic field
Magnetic field forms a pattern of
Concentric circles around a current-carrying wire
When current reverses direction, the direction of the field lines are
Reverse
Right hand rule tells us the direction of
The B-field
Curl hands around the loop in the direction of
Current and thumb gives you direction of the B-field
Magnetic field lines about a current-carrying wire bunch up when the wire is
Bent into a loop
Magnetic field intensity increases as the number of loops increases in a
Current-carrying coil temporary magnet
Electromagnet
Iron bar placed in a current carrying coil
An electromagnet can be made stronger by increasing the
Number of turns of wire and the current in the coil
A current carrying coil of wire is
An electro magnet
The strength of an electromagnet is increased by
Increasing the current through the coil and increasing the number of turns in the coil
Industrial magnets gain additional strength by
Having a piece of iron within the coil
Magnetic domains in the iron core are
Induced into alignment adding to the field
Electromagnets without iron cores are used in
Magnetically levitated or maglev transportation
Levitation is accomplished by
Magnetic coils that run along the track called a guideway
The coil repel large magnets on
The train’s undercarriage
Continually alternating electric current fed to the coils continually alternates their
Magnetic polarity, pulling and pushing the train forward
Moving charges in a magnetic field experience a
Deflecting force
Greatest force
Particle movement in direction perpendicular to the magnetic field lines
Least force
Particle movement other than perpendicular to the magnetic field lines
No force
Particle movement parallel to the magnetic field lines
On moving charged particles: A beam of electrons is deflected by
A magnetic field
Direction is perpendicular to
Both magnetic field lines and current perpendicular to wire
Strongest when current is
Perpendicular to the magnetic field lines
The reason that an electron moving in a magnetic field doesn’t pick up speed is
The magnetic force is always perpendicular to its motion
The magnetic force on a moving charged particle can change the particle’s
Direction
Earth itself is a huge
Magnet
The magnetic pole of Earth are widely separated from
The geographic poles
The magnetic field of Earth is not due to a giant magnet in its interior, it is due to
Electric currents
Most scientists think that moving charges looping around within the molten part of Earth create
The magnetic field
Universe is a shooting gallery of charged particles called
Cosmic rays
They travel through space at fantastic speeds and make up the cosmic radiation that is
Hazardous to astronauts
Cosmic rays are deflected away from Earth by
Earth’s magnetic field
Most of the charged particles (protons and electrons) trapped in
The outer belt probably come from the Sun
Storms on the Sun hurl charged particles out in great fountains, many of which pass
Near Earth and are trapped by its magnetic field
Trapped particles follow corkscrew paths around the magnetic field lines of Earth and bounce between
Earth’s magnetic poles high above the atmosphere
Disturbance in Earth’s field often allow the particles to dip into the atmosphere, causing it
To glow like a fluorescent lamp and this is the beautiful aurora
