CHAPTER 24 Flashcards
What is the source of the
magnetic force?
Electric charges in motion
are the sources of magnetic forces.
The fundamental rule for
the attraction and repulsion of magnets is that
_________.
like poles repel each other while opposite poles attract
What is a very important
difference between electric charges and magnetic poles?
Whereas electric charges
can be isolated, magnetic
poles cannot.
The source of a magnetic field is a moving
_________.
electron
What type of field or fields
surround a moving electron?
Electric field and magnetic
field
How does magnetic field
strength relate to the
closeness of magnetic
field lines about a bar magnet?
The field strength is
stronger where the field
lines are closer.
What produces a magnetic field?
Electric charges in motion
What two kinds of motion
do electrons in an atom appear to have?
Revolution and spin
Magnetic domains are
composed of clustered
_________.
aligned iron atoms
Why is every piece of iron
not a magnet?
Because the domains in
ordinary iron are not
aligned
The magnetic field about
a straight length of
current-carrying wire is
_________.
circular in shape
If a compass is moved
in a circle around a
current-carrying wire, the
needle will be pointing________.
always tangent to the circle
When an iron rod is placed
inside a current-carrying
coil of wire _________.
the coil becomes a
stronger electromagnet
Why are the magnetic fields of superconducting magnets often stronger than
those of conventional magnets?
Conventional magnets based on iron
have a maximum magnetization that occurs when all of the domains are aligned.
This saturation magnetization is weaker than the magnetic field of superconducting coils.
What happens when Dr. Hewitt places a
current- carrying wire between the poles
of the magnet for the first time?
The wire jumps down.
What happens when Dr. Hewitt turns
the magnet around and places the current-carrying wire between the poles of
the magnet for the second time?
The wire jumps up.
What kinds of appliances work on the
principle of deflection of a current-carrying wire in a magnetic field?
electric motor
What happens when a switch is closed
in a circuit that contains a battery and a
wire that is placed between the poles of
a magnet?
The wire will either bend up or down between the poles of the magnet due to the
force of the magnetic field.
What happens to the shape of a wire that
is part of a circuit with a battery when the
switch is closed and the battery voltage
is increased?
The wire bends more than it did before.
What happens to the shape of a wire that
is part of a circuit with a battery when the
switch is closed and the direction of the
current is reversed in the wire?
The wire will bend the same amount but
in the opposite direction.
The force that acts on an electron traveling in a magnetic field is _________.
perpendicular in direction to the magnetic field
The force that acts on a current-carrying wire placed in a magnetic field is
_________.
perpendicular in direction to the magnetic field
Compared with a simple galvanometer,
an electric motor is _________.
much the same with small modifications
The magnetic force that acts on an electric charge at rest is _________.
zero
