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Definitions of Key Words
- Chapter
1
- Work - the
energy
transferred
by a force
- Elastic - a material
able to regain its
shape after it has
been squished or
stretched
- Useful
Energy -
Energy
transferred
to
where
it
is
wanted
in
the
way
it
is
wanted
- Wasted Energy -
Energy that is not
useful transferred
- Dissipation of Energy -
The energy that is not
usefully transferred
and stored in less
useful ways
- Power - The
energy
transformed in
transferred
per seconds.
Measured in
Watts
- Work - the
energy
transferred
by a force
- Chapter 2
- Thermal Conductivity -
Property of a material that
determines the energy
transfer through it by
conduction
- Infrared
Radiation -
Electromagnetic
waves between
microwaves and
visible light on
the
electromagnetic
scale
- Black Body
Radiation -
The
radiation
emitted
from a
perfect
black body
- Perfect
Black
Body -
a body
that
absorbs
all the
radiation
that
hits
it
- Specific Heat
Capacity -
Energy needed to
raise the
temperature of
1kg of a
substance by 1'C
- Thermal Conductivity -
Property of a material that
determines the energy
transfer through it by
conduction
- Chapter 3
- Biofuel -
Any fuel
taking
from
living or
recently
living
materials
(e.g.
animal
waste)
- Renewable Energy -
Energy from natural
sources that is
always being
replenished so never
runs out
- Carbon-neutral - A biofuel from a living
organism that takes in as much carbon
dioxide from the atmosphere as is
released when the fuel is burned
- Nuclear
Fuel -
Substance
used in
nuclear
reactors
that
releases
energy
due to
nuclear
fission
- Nucleus -
tiny
positively
charged
object
composed
of
protons
and
neutrons
at
the
centre
of
every
atom
- Reactor
Core - The
thick steel
vessel
used to
contain
fuel rods,
control
rods and
the
moderator
in a
nuclear
fission
reactor
- Geothermal
Energy -
Energy that
comes from
energy
released by
radioactive
substances
deep within
the Earth
- Biofuel -
Any fuel
taking
from
living or
recently
living
materials
(e.g.
animal
waste)
- Chapter 4
- Protons -
positively
charged
particles
- Neutrons
-
Uncharged
particles
- Ion -
A
charged
atom
- Electric Field - A field around
a charged object which
causes a non-contact force
on any other charged objects
in its field
- Electrons
- Tiny
negatively
charged
particles
- Series -
Components
connected in a
circuit such that
the same
current passes
through them
all
- Potential
Difference -
The
difference
of electrical
potential
between
two points.
It is
measured in
Volts
- Parallel -
Components
connected in
a circuit such
that the
potential
difference is
the same
for all
- Resistance
-
The
potential
difference
divided
by
the
current
passing
through
the
component.
It
is
measured
in
Ohms
- Diode - A non-ohmic conductor
that has a much higher
resistance in its reverse
direction than its forward
direction
- Light Emitting
Diode - A diode
that emits light
when it
conducts
- Thermistor - A
resistor whose
resistance depends
on its temperature
- Light Depending Resistor - A
resistor whose resistance
depends on the intensity of the
light incident on it
- Protons -
positively
charged
particles
- Chapter 5
- Direct Current -
Electric current in
a circuit that is in
one direction only
- Alternating Current -
Electric current in a
circuit that repeatedly
reverses its direction
- Live Wire - The
mains wire
that has a
voltage
- Neutral Wire - The wire
of a mains circuit that is
earthed at the local
substation so its
potential is close to zero
- Oscilloscope -
A device used
to display the
shape of an
electrical wave
- Earth Wire - The wire in
a mains cable used to
connect the metal case
of an appliance to earth
- Fuse - contains a
thin wire that melts
and cuts the
current off if too
much current
passes through it
- Direct Current -
Electric current in
a circuit that is in
one direction only
- Chapter 6
- Density - Mass per
unit volume of a
substance
- Physical Changes - A change
in which no new substances
are produced
- Melting point -
Temperature at which a
pure substance melt or
freezes
- Boiling Point
-
Temperature
at which a
pure
substance
boils or
condenses
- Freezing Point - The temperature at which a pure substance freezes
- Latent Heat - The energy transferred to or from a
substance when it changes its state
- Internal Energy - The energy of the particles of a
substance due to their individual motion and positions
- Specific Latent Heat of Fusion - Energy needed to melt
1kg of a substance with no change of temperature
- Specific Latent Heat of Vaporisation - Energy
needed to boil away 1kg of a substance with no
change of temperature
- Density - Mass per
unit volume of a
substance
- Chapter 7
- Alpha Radiation - Alpha
particles, each composed
of two protons and two
neutrons, emitted by
unstable nuclei
- Beta Radiation - Beta
particles that are
high-energy electrons
created in, and emitted,
from unstable nuclei
- Gamma Radiation -
Electromagnetic radiation
emitted from unstable
nuclei in radioactive
substances
- Atomic
Number -
the
number
of protons
in an
atom
- Mass Number - The
number of protons and
neutrons in an atom
- Isotopes - Atoms with the same
number of protons but different
numbers of neutrons
- Ionisation - Any
process in
which atoms
become charged
- Irradiated - An object
that has been exposed
to ionising radiation
- Activity
- The
number
of
unstable
atoms
that
decay
per
second
in
a
radioactive
source
- Count Rate
- The
number of
counts per
second
detected by
a Geiger
counter
- Half-life -
Average
time
taken for
the
number
of nuclei
of the
isotope (or
mass of
the
isotope) in
a sample
to halve
- Nuclear Fission -
The process in
which certain
nuclei
(uranium-235
and
Plutonium-239)
split into two
fragments,
releasing energy
and two or three
neutrons as a
result
- Chain
Reaction -
Reactions
in which
one
reaction
causes
further
reactions,
which in
turn
cause
further
reactions
- Moderator -
Substance in a
nuclear reactor
that slows down
fission neutrons
- Nuclear Fusion -
The process where
small nuclei are
forced together to
fuse and form a
larger nucleus
- Alpha Radiation - Alpha
particles, each composed
of two protons and two
neutrons, emitted by
unstable nuclei
- Chapter 8
- Displacement - Distance in a given direction
- Vector - A physical quantity that has a
magnitude and a direction (e.g. displacement)
- Scalar - A
physical
quantity
that has
magnitude
only (e.g.
mass)
- Magnitude - The size or amount of a physical quantity
- Forces - Can
change the motion
of an object.
Measure in N,
newtons
- Newton's Third Law -
When two objects interact
with each other, they exert
equal and opposite forces
on each other
- Friction - The force opposing the relative motion
of two solid surfaces in contact
- Resultant
Force - A
single force
that has the
same effect as
all the forces
acting on the
object
- Newton's First
Law of Motion -
If the resultant
force on an object
is zero, the object
stays at rest if it
is stationary, or
it keeps moving
with the same
speed in the
same direction
- Moment
-
The
turning
effect
of
a
force
- Load - The
weight of
an object
raised by
a device
used to
lift the
object, or
the force
applied by
a device
when it is
used to
shift an
object
- Principle of Moments - For an
object in equilibrium, the sum
of all the clockwise moments
about any point = the sum of
all the anti-clockwise moments
about that point
- Parallelogram of
forces - A
geometrical
method used to
find the resultant
of two forces that
do not act along
the same line
- Displacement - Distance in a given direction
- Chapter 9
- Velocity -
Speed in a
given
direction.
Measured
in m/s
- Acceleration -
Change of
velocity per
second.
Measured in
m/s²
- Deceleration
- Change of
velocity per
second
when an
object slows
down
- Velocity -
Speed in a
given
direction.
Measured
in m/s
- Chapter 10
- Newton's Second Law of
Motion - The acceleration of
an object is proportional to
the resultant force on the
object, and inversely
proportional to the mass of
the object
- Inertia -
The
tendency
of an
object to
stay at
rest or to
continue
in
uniform
motion
- Weight -
The force
of gravity
on an
object.
- Mass - The quantity
of matter in an
object, a measure of
the difficulty of
changing the motion
of an object.
Measured in kg
- Gravitational
Field
Strength -
The force of
gravity of an
object of
mass 1kg
and also the
acceleration
of free fall.
Measured in
N/kg
- Terminal
Velocity - The
velocity
reached by an
object when
the drag force
on it is equal
and opposite
to the force
making it
move
- Stopping Distance -
The distance travelled
by the vehicle in the
time it takes for the
driver to think and
brake
- Thinking
Distance
- The
distance
travelled
by the
vehicle in
the time
it takes
the
driver to
react
- Braking
Distance
- The
distance
travelled
by a
vehicle
during
the time
it takes
for its
brakes to
act
- Conservation
of
Momentum -
In a closed
system the
total
momentum
before an
event is
equal to the
total
momentum
after the
event.
- Extension - The
increase in
length of a
spring from its
original length
- Limit of Proportionality - The limit for
Hooke's law applied to the extension
of a stretched spring
- Newton's Second Law of
Motion - The acceleration of
an object is proportional to
the resultant force on the
object, and inversely
proportional to the mass of
the object
- Chapter 11
- Pressure - Force per unit
area. Measure in Pa
(Pascals) or N/m²
- Pressure - Force per unit
area. Measure in Pa
(Pascals) or N/m²
- Chapter 12
- Mechanical
Waves
-
Vibration
that
travels
through
a
substance
- Electromagnetic
Waves - Electric
and magnetic
disturbances
that transfer
energy from one
place to another
- Transverse
Waves - A wave
whose
oscillations are
perpendicular to
the direction of
energy transfer
- Longitudinal
Waves - Waves
whose oscillations
are parallel to the
direction of
energy transfer
- Compression -
Squeezing together
- Refraction - The
change of
direction of a
light ray when it
passes across a
boundary
between two
transparent
substances
- Wavelength
- The
distance
from one
wave crest
to the next
- Amplitude - The
maximum distance
moved by an
oscillating object
from its equilibrium
position
- Frequency - The
number of wave
crests passing a
fixed point every
second
- Speed - The
distance travelled
by each wave
every second
through a
medium
- Reflection -
The change
of direction
of a light
ray or wave
when it
passes
across a
boundary
when the
ray or wave
stay in the
incident
medium
- Transmission -
a wave passing
through a
substance
- Echo -
Reflection
of
a
sound
that
can
be
heard
- Ultrasound
Waves -
Sound
waves at
frequency
greater
than
20000Hz
- Seismic
Waves
-
Shock
waves
that
travel
through
the
Earth
and
across
its
surface
as
a
result
of
an
earthquake
- Mechanical
Waves
-
Vibration
that
travels
through
a
substance
- Chapter 13
- Radio Waves - Electromagnetic waves
of wavelength greater than 0.10m
- Microwaves - Electromagnetic
waves between infrared and
radio waves in the
electromagnetic spectrum
- Infrared
Radiation -
Electromagnetic
waves
between
visible
light
and
microwaves
on
the
electromagnetic
spectrum
- Ultraviolet
Radiation -
Electromagnetic
waves between
visible light and
x-rays on the
electromagnetic
spectrum
- X-Rays -
Electromagnetic
waves smaller
in length than
ultraviolet
waves
- White Light - Light
that includes all the
colours of the
spectrum
- Carrier
Waves -
Waves
used to
carry an
type of
signal
- Contrast
Medium - An
x-ray absorbing
substance used
to fill a body
organ so it can
be seen on a
radiograph
- Charge Couple Device - An
electronic device that creates
an electronic signal from an
optical image formed on the
CCD's array of pixels
- Radiation Dose - Amount
of ionising radiation a
person receives
- Radio Waves - Electromagnetic waves
of wavelength greater than 0.10m
- Chapter 14
- Normal - Straight line through a
surface or boundary perpendicular to
the surface or boundary
- Angle of Incidence -
Angle between the
incident ray and the
normal
- Angle of
Reflection -
Angle between
reflected ray
and the
normal
- Virtual
Image - An
image seen
in a lens or
a mirror,
from which
light rays
appear to
come after
being
refracted
by a lens
or reflected
by a mirror
- Specular Reflection -
Reflection from a
smooth surface
where each ray is
reflected in the same
direction
- Diffuse Reflection - Reflection from a rough
surface so the rays are scattered in different
directions
- Convex Lens - A lens that
makes the light rays parallel to
the principal axis converge at a
point
- Principal Focus - The
point where light
rays parallel to the
principal axis of a
lens are focused
- Magnifying Glass - A
converging lens used to
magnify small objects
which must be placed
between the lens and
its focal point
- Concave Lens - A
lens that makes
light rays parallel
to the axis
diverge
- Normal - Straight line through a
surface or boundary perpendicular to
the surface or boundary
- Chapter
15
- Magnetic Field
- The space
around a
magnet or a
current-carrying
wire
- Electromagnet - An insulated
wire wrapped round an iron
bar that becomes magnetic
when there is a current in the
wire
- Motor Effect - When a current is
passed along a wire in a magnetic
field, and the wire is not parallel to
the lines of the magnetic field, a
force is exerted on the wire by the
magnetic field
- Fleming's left-hand Rule - Gives the
direction of a force on a
current-carrying wire in a magnetic
field according to the directions of the
current and the field
- Solenoid - A long coil
of wire that produces
a magnetic field in and
around the coil when
there is a current
through it
- Electromagnetic Induction - The process of
inducing a potential difference in a wire by
moving the wire so it cuts across the lines
of flux
- Generator Effect - The
production of a potential
difference using a
magnetic field
- Alternator -
An
alternating
current
generator
- Dynamo - A
direct current
generator
- Transformer -
Electrical device
used to change
an alternating
voltage
- Step-up Transformer - Transformer used to increase the size of the alternating voltage
- Step-down Transformer
- Transformer used to
decrease the size of the
alternating voltage
- Magnetic Field
- The space
around a
magnet or a
current-carrying
wire
- Chapter 16
- Protostar - The
concentration
of dust clouds
and gas in
space that
forms a star
- Main Sequence -
The main
sequence is the
life stage of a star
during which it
radiates energy
because of fusion
of hydrogen nuclei
in its core
- Red Giant - A
star that has
expanded and
cooled, resulting
in it becoming
red and much
larger and cooler
than it was
before it
expanded
- White Dwarf - A
star that has
collapsed from
the red giant
stage to become
much hotter and
denser
- Black Dwarf
- A star that
has faded
out and gone
cold
- Red Supergiant - A star much
more massive than the Sun will
swell out after the main
sequence stage to become a red
supergiant before it collapses
- Supernova - The
explosion of a massive
star after fusion in its
core ceases and the
matter surrounding its
core collapses on to the
core and rebounds
- Neutron Star - The highly
compressed core of a massive
star that remains after a
supernova explosion
- Black Hole -
An object in
space that has
so much mass
that nothing,
not even light,
can escape
from its
gravitational
field
- Centripetal
Force - The
resultant
force
towards the
centre of a
circle acting
on an object
moving in a
circular path
- Redshift - Increase in the
wavelength of
electromagnetic waves
emitted by a star or
galaxy due to its motion
away from us. The faster
the speed of the star or
galaxy, the greater its
redshift
- Big Bang Theory - The
theory that the universe
was created in a massive
explosion and that the
universe has been
expanding ever since
- Cosmic Microwave
Background Radiation -
Electromagnetic radiation
that has been travelling
through space ever since it
was created shortly after the
big bang
- Dark Matter - Matter in
a galaxy that cannot be
seen. Its presence is
deduced because
galaxies would spin
much faster if their
stars were their only
matter
- Protostar - The
concentration
of dust clouds
and gas in
space that
forms a star
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