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Cards (92)
what is a magnetic field?
region
surrounding a magnet where another magnet or magnetic
material
experiences a
non-contact
force
what does a magnetic compass contain?
a small
bar
magnet that points in the direction of the
earths
magnetic
field
what is produced when current flows through a conducting wire?
magnetic field
produced around the wire
what determines the strength of the magnetic field around a current-carrying wire?
the
magnitude
of the
current
flowing through the wire
the
distance
from the wire
what is a solenoid?
a
coil
of wire which when
current
passes through creates a strong
magnetic field
describe the magnetic field found inside the solenoid
strong
and
uniform
what is an electromagnet?
a
solenoid
with an added
iron
core
adding the iron core increases the
strength
of the
magnetic
field
what is the motor effect?
when a
force
is exerted between a
magnetic
field and a
current-carrying
conductor placed in that field
what factors affect the size of the force on a current-carrying wire in a magnetic field?
the
magnitude
of the
current
flowing through the
conductor
the
strength
of the
magnetic field
that the
conductor
is placed in
if the direction of current in a current-carrying wire placed in a uniform magnetic field is reversed what happens to the force?
direction
of the
force
is
reversed
if the strength of the current in a current carrying wire is increased what happens to the force?
the
strength
of the force is
increased
what criteria must be met for the equation linking force, magnetic flux density, current and length to hold?
conductor must be at
right-angles
to the
magnetic field
it is placed in
what is the unit for magnetic flux density?
Tesla
,
T
How does an electric motor work?
coil of wire, carrying a
current
is placed in a
magnetic field
forces
on the two sides
perpendicular
to the field experience forces in
opposite
directions
causes a
rotational
effect
how do loudspeakers make use of the motor effect?
used to convert
variations
in the current of an
electrical
circuit into the
pressure
variations which produce
audible
sound
explain how a loudspeaker works
cone
with a
wire
wrapped around it connected to an
a.c
power supply & placed in a
permanent
magnetic field
when
current
flows through the wire, creates a
second
magnetic field which interacts with the
permanent
field
produces a
force
which causes the cone to
vibrate
how is the pitch of sound changed in a loudspeaker?
frequency
of the
a.c
current is
altered
creates a different
frequency
of
vibration
in the
cone
give two examples of transverse waves:
em
waves
seismic
s-waves
give two examples of longitudinal waves
sound
waves
seismic
p-waves
what are the two parts of a longitudinal wave called?
compressions
and
rarefactions
what is a waves amplitude?
maximum displacement
of a
point
on a wave from its
undisturbed
position
what is the unit used for frequency?
Hertz
,
Hz
what is wave speed?
speed at which the wave
moves
or at which
energy
is
transferred
through a
medium
what does a wave transfer?
energy
what word is used to describe when a wave bounces off a surface?
reflection
how do sound waves travel through a solid?
particles
in the solid
vibrate
and transfer
kinetic
energy through the
material
what is the frequency range of human hearing?
20Hz
-
20kHz
what are ultrasound waves?
waves which have a
higher frequency
than the
upper
human limit of
hearing
give an example use for ultrasound waves
medical
or
industrial
imaging
what natural event causes seismic waves to be produced?
earthquakes
produce both
p-waves
and
s-waves
what medium do p-waves travel through?
solids
and
liquids
what medium do s-waves travel through?
solids
what technique is used to detect objects in deep water and measure water depth?
echo
sounding
high
frequency sound waves are
emitted
,
reflected
and
detected
time
difference between
emission
and
detection
alongside wave
speed
are used to calculate
distances
what type of spectrum do em waves form?
continuous
how do the speeds of em radiation differ in a vacuum and in air?
same
speed
what property of waves in different mediums causes refraction?
velocity
wave speed
slower
in
denser
materials, causing
refraction
in which direction do waves refract when entering a denser medium?
bend
towards
the
normal
angle of refraction is
less
than the angle of
incidence
what type of waves can be produced by oscillations in an electrical circuit?
radio
waves
how can radio waves create an alternating current in a circuit?
when radio waves
absorbed
they can induce
oscillations
in a
circuit
with the same
frequency
as the
waves
themselves
where do gamma rays originate from?
changes in the
nuclei
of atoms
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