Chapter 24: Magnetism Flashcards
The source of all magnetism is: a) tiny pieces of iron; b) tiny domains of aligned atoms; c) ferromagnetic materials; d) moving electric charge; e) none of these.
d) moving electric charge
Moving electric charges will interact with
an electric field or a magnetic field.
An iron rod becomes magnetic when
the net spins of its electrons are in the same direction.
Magnetic field lines about a current-carrying wire: a) extend radially from the wire; b) circle the wire in closed loops; c) parallel the length of the wire; d) choices a and b are both correct.
b) circle the wire in closed loops
Which pole of a compass needle points to a south pole of a magnet?
north pole
An iron nail is more strongly attracted to the
north or south pole–no difference really.
Pigeons navigate primarily by
magnetic sensors in their heads.
Pigeons have a magnetic sense, and not only can they discern longitudinal directions along Earth’s magnetic field, they can also detect latitude by the dip of Earth’s field.
The intensity of cosmic rays bombarding the Earth’s surface is largest at the: a) poles; b) mid-latitudes; c) equator.
a) poles
Superconducting electromagnets: a) exist now; b) may be possible in the near future; c) may be possible in the distant future; d) are science fiction.
a) exist now
If a steady magnetic field exerts a force on a moving charge, that force is directed
at right angles to the direction of the motion.
Which force field can accelerate an electron, but never change its speed: a) electric field; b) magnetic field; c) both of these; d) none of these.
b) magnetic field
Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a: a) north pole; b) south pole; c) north or south pole–no difference really.
a) north pole
Magnetic compasses apparently were first used by: a) Columbus; b) Greeks; c) Australian aborigines; d) Vikings; e) pigeons, then Chinese.
e) pigeons, then Chinese.
Magnetic domains normally occur in; a) iron; b) copper; c) silver; d) all of these; e) none of these.
a) iron
If a compass is moved from the northern hemisphere to the southern hemisphere, its magnetic needle will change direction: a) by 180 degrees; b) depending on where the measurement is taken; c) by 90 degrees; d) hardly at all; e) none of these.
d) hardly at all
Between magnets, it is the attraction of unlike magnetic poles for each other and the repulsion between like magnetic poles (def).
Magnetic force.
In all magnets—can’t have one pole without the other. No single pole known to exist.
Between a magnetic field and a moving charged particle, it is a deflecting force due to the motion of the particle (def).
Magnetic force
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.
Magnetic force
The region of magnetic influence around a magnetic pole or a moving charged particle (def).
Magnetic field
Clustered regions of aligned magnetic atoms (def).
Magnetic domains
When these regions themselves are aligned with one another, the substance containing them is a magnet.
A magnet whose field is produced by an electric current (def).
Electromagnet
It is usually in the form of a wire coil with a piece of iron inside the coil. Electromagnets without iron cores are used in magnetically levitated, or “maglev,” transportation.
Various high-speed particles that travel throughout the universe (def).
Cosmic rays;
The universe is a shooting gallery of charged particles called cosmic rays.
A weak and strong magnet repel each other. The greater repelling force is by the: a) stronger magnet; b) weaker magnet; c) both the same; d) none of the above.
c) both the same; (Remember Newton’s third law!)
Where magnetic field lines are more dense, the field there is: a) weaker; b) stronger; c) both A and B; d) neither A nor B.
b) stronger;
Strength indicated by closeness of the lines: lines close together indicates strong magnetic field; lines farther apart indicates weak magnetic field.
The source of all magnetism is: a) electrons rotating around an atomic nucleus; b) electrons spinning around internal axes; c) either or both A and B; d) tiny bits of iron.
c) either or both A and B
What are the two kinds of electron motion which produce a magnetic field?
Electron spin and electron revolution
When alignment of domains remains once external magnetic field is removed?
Permanent magnet;
Permanent magnets are made by placing pieces of iron or similar magnetic materials in a strong magnetic field or by stroking material with a magnet to align the domains..
When alignment of domains returns to random arrangement once external magnetic field is removed?
Temporary magnet
Magnetic field forms a pattern of ________ _______ around a current-carrying wire.
concentric circles
An electromagnet can be made stronger by: a) increasing the number of turns of wire; b) increasing the current in the coil; c) both A and B; d) none of the above.
c) both A and B
The magnetic field of Earth is not due to a giant magnet in its interior—it is due to
electric currents.
Most Earth scientists think that moving charges looping around within the molten part of Earth create the
magnetic field.
Earth’s magnetic field reverses direction: 20 reversals in last 5 million years.
___________ in Earth’s field often allow the ions to dip into the atmosphere, causing it to glow like a fluorescent lamp. Hence the aurora borealis or aurora australis.
Disturbances
Storms on the Sun hurl _______ _________ out in great fountains, many of which pass near Earth and are trapped by its magnetic field.
charged particles
The trapped particles follow corkscrew paths around the magnetic field lines of Earth and bounce between Earth’s magnetic poles high above the atmosphere.
