Physics Flashcards
Define conduction
transfer of thermal energy through a metal
How does the motion of gas particles changes when they are cooled?
slow down
Describe thermal conduction in a metal by electrons
electrons move freely throughout metal
Difference between boiling and evaporation (2)
boiling occurs throughout liquid
evaporation occurs at surface only
Technique to prevent energy loss from windows
double glazing - air between 2 panes of glass
Technique to prevent energy loss from floors
carpet
Technique to prevent energy loss from roof
loft insulation - insulation on top of ceiling prevents heat loss by conduction and convection
Technique to prevent energy loss from walls
cavity wall - 2 single walls separated by air prevents conduction
Does radiation need particles
no
Define boyle’s law
when temperature of gas stays constant, volume of gas inversely proportional to pressure
Define condensation
when substance changes from gas to liquid
Define boiling point
temperature which substance changes from liquid to gas
Define solidification
when substance changes from liquid to solid
Define melting point
temperature which it changes from solid to liquid
Factors that increase rate of evaporation (3)
higher temperatures
strong flow of air across surface
increased surface area
Define evaporation
when particles break away from liquid surface and form a gas/vapour
Define the brownian motion (2)
random motion of particles
large particles constantly hit by small fast particles
Motion of gas particles (2)
random + fast motion
collide with other particles/walls
Motion of liquid particles
slide over each other
Motion of solid particles
vibrate in place
Arrangement of gas particles (3)
irregular
widely spaced
particles able to move freely
Arrangement of liquid particles (3)
irregular
closely packed together
particles able to slide over each other
Arrangement of solid particles (3)
regular pattern
closely packed together
particles held in place
Properties of gases (4)
assumes shape of container
assumes volume of container
can be compressed
flows easily
Properties of liquid (3)
assumes shape of container
is not easily compressible
flows easily
Properties of solids (4)
fixed volume
fixed shape
not easily compressible
does not flow easily
The hotter an object is the more infra red they emit. True or False?
true
What do all objects emit
infra red radiation
Describe the convection cycle (5)
particles in area heated making fluid less dense
less dense liquid rises
particles’ KE converted GPE so temperature lost
as temperature lost particles need less space and become denser
cold particles fall to bottom
Why do metals conduct easier (2)
have free electrons
electrons can pass along metal allowing energy to transfer easily
Why are gases the worst conductors
their particles are far apart
Which state is the worst conductor of heat
gas
Why are solids the best conductors
their particles are close together
Which state is the best conductor of heat
solids
Define conduction (2)
method of heat transfer in solids, liquids, gas
transfers heat when vibrating particles bounce into each other
What increases the pressure of a gas (2)
increased temperature
decreased volume of sealed container
Why might a container implode (6)
Ambient temperature decrease inside
Kinetic energy of gas molecules decreases
Fewer collisions
Gas pressure decreases
gas pressure greater outside than inside
therefore big container implodes
What happens when work is done on a gas (2)
increases internal energy
increases temperature of gas
Why does an increase in temperature increase pressure (3)
increases kinetic energy of particles
average speed of molecules increased
will hit surface more often and with greater force
What does an increase in temperature do to pressure
increases pressure
How does a car tire keep inflated (3)
gas particles collide with tire walls
pressure created (force over area)
pressure inflates tire
Pressure formula
force/area
Define range
difference between hottest and coldest that can be measured
Define sensitivity
smallest change that can be measured
Define linearity
if liquid expands by same amount for each temperature increase
Explain contraction of gases (2)
contracts once cooled
particles move back to original positions
Explain expansion of gases (2)
easier to expand as gas particles far apart
distance between particles increase when heated
Why do liquids contract when cooled
particles move less
Why do liquids expand when heated
particles move more and need more space
What liquids expand and contract in thermometers (2)
mercury
alcohol
What happens when a solid is cooled
gets smaller/contracts
What happens when a solid is heated
gets bigger/expands
How does sweat help to cool us down (2)
energy taken when water molecules evaporate
cools skin
How evaporation works (4)
molecules move at different speeds
faster molecules in liquid escape liquid as gas
lowers average speed of remaining particles
cools substance down
What happens to atmospheric pressure as elevation above sea increases
decreases
What does an increase in energy cause for a system (2)
raises temperature
changes state
How does heating change the energy stored within a system
increases energy of particles
Define internal energy
energy stored in system
Are physical reactions easily reversible
yes
What is conserved when a substance changes state
mass
What increases as you go from solid to liquid (2)
volume
kinetic energy
Is nuclear energy renewable?
no
What energy do fossil fuels store
chemical energy
Examples of fossil fuels (3)
coal
oil
gas
Fossil fuels definition
carbon-based materials formed over millions of years from remains of plants and animals
cons of biomass energy
large area of land needed to grow trees
Pros of biomass energy (3)
doesn’t add to greenhouse effect
doesn’t need special equipment
renewable as long as we replace trees cut down
Biomass energy description (4)
chemical potential energy stored in live things can be converted to heat energy by burning them
trees absorb sun energy
Trees change energy into chemical energy
burning trees turns this energy into heat
Cons of wind energy (2)
only works if windy
can be ugly and noisy
Pros of wind energy (3)
renewable
no pollution as nothing is burned
quite cheap and easy to build
Cons of solar energy (2)
solar cells and panels are expensive
only works if sunny
Pros of solar energy (2)
renewable
no pollution as nothing gets burned
Application of solar energy (2)
energy from sun can be changed into electrical energy to power homes using solar cells
solar panels can use solar energy to heat water for homes
Solar energy description
earth gets heat and light energy from sun
Cons of tidal energy (2)
costs money to build dam
dam can cause local flooding
Pros of tidal energy (3)
renewable
cheap to run
reliable since there are always 2 tides every day
How does tidal energy work(3)
high tide has gravitational energy
at high tide water trapped behind dam
at ow tide water releases and generates electricity
Hydroelectric cons (3)
large area of land needed
damages wildlife habitats
dam can cause population displacement as it changes where water naturally flows
Hydroelectric pros (3)
renewable
no pollution - nothing gets burned
can store water and let water out when we need electricity
Cons of wave energy (3)
machines can be damaged by storm
require lots of machines to get reasonable amount of energy
machines cost a lot of money
Pros of wave energy (2)
renewable
no pollution as nothing gets burned
Description of Wave energy (2)
sea waves have kinetic energy
machines bob up and down in waves generating electricity
Disadvantages of geothermal (2)
few places in the world to do this
cost money to drill into ground
Benefits of geothermal (3)
renewable
no pollution as nothing gets burned
doesn’t damage environment
What is energy efficiency? (2)
measure of how well device transfers energy into form we want
proportion of input energy which device transforms into useful output energy
Can energy be created or destroyed?
no - only transferred
What is energy
ability to make something happen
Efficiency formula
(useful energy output/energy input) x 100
How does nuclear fission work
splitting nucleus releases stored energy
How does geothermal power work (3)
cold water pumped below ground
hot rocks heat water into steam
steam generates electricity
How does solar power work (2)
solar cells convert light energy to electrical energy
electric current charges battery that stores chemical potential energy
How does hydroelectric power work (4)
water flows through pipe to turbines
water turns turbine
turbine drives generator
generator produces electricity
How does wind power work (2)
kinetic energy of wind rotates blades
blades turn turbines that generate electricity
Define non-renewable
energy sources which cannot be replaced once used up
Power station steps (5)
fuel burned and steam produced in boiler
steam turns turbine
turbine drives generator
generator produces electricity
electricity supplied to homes, industry
Where do we obtain most of our energy
fossil fuels (coal, oil gas)
Measurment of power
watts (W)
Power formula
work done (Joules)/time taken (s)
Define power
the rate of doing work/transferring energy
What is the law of conservation of mass
energy cannot be created or destroyed
Define sound energy (2)
transfer small amount of energy from the source of the noise
sound vibrates air particles as a longitudinal wave
Define light energy
light waves transfer energy to the object the light strikes (absorbed by)
Define electrical energy
electrical currents transfer electricity to different places
Define thermal energy
heat energy contained within an object
Define nuclear energy
energy stored between strong bonds of nucleus
Define chemical potential energy (2)
energy stored in atomic forces/bonds
energy can be transferred by breaking the bonds
Define elastic potential energy
energy stored in stretched objects
Define kinetic energy
energy stored by a moving object
Define gravitational potential energy
energy stored by an object raised up in a gravitational field
Formula for amount of kinetic energy stored
1/2 x mass (kg) x velocity^2 (m/s)
Formula for gravitational potential energy
mass (kg) x acceleration due to gravity (10) x height above ground (m)
Energy used to describe stored potential energy transferred to movement energy
kinetic energy
When a load is raised above the ground what energy will it gain
gravitational potential energy
When stretching or compressing a spring what energy will it have
elastic potential energy
Define potential energy
stored or hidden energy
When an object is lifted vertically, what does the amount of work done depend on? (2)
weight of the object
vertical distance it moves
When an object is lifted vertically, what is the force moved?
the weight of the object
Formula for work
work done = force x distance travelled in direction of force
Unit of work
joules (J)
What does the amount of work depend on (2)
magnitude of force
distance moved in the direction of force
What is work (2)
energy transferred
application of force which results in movement
Amplitude of sound wave
loudness of sound
Frequency of sound wave
pitch of sound wave
Range of human hearing
20Hz - 20,000 Hz
Uses of microwaves (2)
radar
cooking
Features of microwaves (2)
largest wavelengths
least amount of frequency/energy
Dangers of UV rays (2)
can damage surface cells of body
can cause blindness or skin cancer
Infrared radiation damage
can burn skin/body tissue
Speed which all electromagnetic waves travel in a vacuum
3 x 10^8
Features of infrared radiation (4)
emitted by all objects
hotter objects emit more than cold
3rd largest wavelength
4th greatest energy/frequency
Features of ultraviolet rays (3)
component of sun rays
3rd shortest wavelength
3rd greatest energy/frequency
Uses of X-rays (2)
treat cancer - destroy tumour cells
screen baggage/scan objects - different materials absorb different amounts of X-rays
Features of X-rays (3)
second greatest energy/frequency
second shortest wavelength
produced when high-energy electrons fired at target
Use of gamma rays (2)
radiotherapy - kill cancer cells
tracer - track substances in biological systems
Features of gamma rays (3)
shortest wavelength
greatest frequency/energy
can cause cancer/mutation in cells
Define a real image (5)
inverted
diminished
closer to lens than distance of object from lens
image where ray actually passes
can be picked up on suitable screen
Define the focal length
distance between lens and principal focus
Define the principal focus
point where parallel light rays all cross over
Features of convex(converging) lenses
cause parallel light rays to converge to one point
Define total internal reflection
at greater angles of incidence, rays entirely reflected back inside medium
Refractive index formula critical angle
1/sin(critical angle)
Define the critical angle
angle of incidence which angle of refraction becomes 90 degrees
Speed of light in vacuum
3 x 10^8
Refractive index of vacuu
1
Refractive index formula (2)
sin(angle of incidence) / sin (angle of refraction)
speed of light in vacuum (air) / speed of light in material
Define the refractive index
indicates
by how much a material changes direction of light
Define the angle of refraction
angle between refracted light ray and normal to surface
Define the angle of incidence
angle between incident light ray and normal to surface
Refraction of light (4)
light waves slow down when travel into material
at angle to glass = rays bend toward normal
rays travel out material = speed increases, bend away from normal
material has parallel sides = light resumes original direction
Formula for angles of incidence/reflection
angle of incidence = angle of reflection measured to a normal when mirror reflects light
Define a virtual image (5)
upright
larger than object
further from lens than distance of object from lens
cannot be projected on screen
rays do not actually pass
Define laterally inversion (2)
left and right exchanged
e.g in mirror
Features of light (2)
does not need medium to travel through
transverse
Define diffraction
when wavefronts change shape when they go through gap
Explain refraction (3)
wave slows down –> wavefronts crowd together –> wavelength shortens
wave strikes boundary ay angle –> part of wave slows down or speed up first
wavefronts go closer together and changes direction
Define refraction
wave enters new medium at angle = wavefronts change direction
Wave speed measurment
m/s
Formula for wave speed
frequency(Hz) x wavelength(m)
Define transverse wave
vibrations are at right angles to direction of wave travel
Amplitude of longitudinal wave
maximum displacement of medium’s vibration from undisturbed position
Wavelength of longitudinal wave
distance between 2 consecutive points of maximum compression
Example of longitudinal waves
sound
Define compression
regions where wave is squashed together
Define rarefaction
regions where wave is spread out
Define longitudinal wave
vibrations in direction of wave travel
Define wavefront
moving line that joins all points on crest
Define amplitude (2)
height of half the crest/trough
maximum displacement of wave from undisturbed position
Define frequency
number of complete waves that go past each second
Define wavelength
distance between 2 adjacent peaks/troughs of wave
Define pressure (3)
how spread out a force is
ratio of force to area
force(N)/area (m^2)
Define stable equilibrium
object that is difficult to topple
How to calculate centre of mass (5)
hang object
suspend mass from same place using thread
mark position of thread
repeat at different place
centre of mass where 2 lines meet
When will an object fall
centre of mass outside pivot
Define centre of mass
one point where body mass all concentrated
Define the principle of moments (3)
if object not turning
sum of clockwise moments about pivot
= sum of anticlockwise moments about pivot
Define the turning effect of a force (2)
moment of the force
force (N) x perpendicular distance from pivot (m)
Define Newton’s 3rd law
forces always come in pairs
Formula for force
mass (kg) x acceleration (m/s^2)
What will happen to the object if the forces are balanced (2)
object will be stationary
object will move at constant speed
Define newton’s first law of motion
resultant force required to change the way something is moving
one form of friction
air resistance
Define friction
force between 2 surfaces which impedes motion and causes heating
Hooke’s law formula
force (N) = spring constant (n/m) x extension of spring (m)
Define hooke’s law
as force of weight increases = extension will proportionally increase until a certain limit
Define the limit of proportionality
point where extension no longer proportional to load
Effects of a force (3)
change object size
change object motion
change object shape
Define a force
push or pull
Density formula
mass (kg) / volume (m^3)
Earth gravitational field
10N/kg
weight measurement
newtons
Formula for weight
mass (kg) x gravitational field strength (N)
Distance from speed time graph
area under curve
graph for increasing acceleration
curved upwards exponential
Graph for steady acceleration
linear upward
Graph for steady speed
horizontal
Graph for acceleration
curved exponential upward
Graph for speed
linear upward sloping
Formula for acceleration (m/s^2)
change in velocity (m/s) / time taken (s)
Formula for speed (m/s)
distance (m)/time (s)
Circuit symbol for variable resistor
rectangle with arrow through
Circuit symbol for battery
- |I—|I-
Circuit symbol for fuse
rectangle with line through
Circuit symbol for Cell
- |I-
Define a magnetic field (3)
region of space where their magnetism affects other objects
lines which move away from north pole to south
more concentrated field lines = stronger magnet
How do some modern alloys become magnetised (2)
magnetic field applied to molten alloy at high temp.
alloy solidifies while in magnetic field
How can a steel bar be magnetised (2)
stroking it with strong magnet
placing bar north and hammering it
How can permanent magnets become magnetized using electricity
large direct current running through coil of wire
Magnet will not continue to attract soft magnetic material even when material is turned around
True or False?
False
What happens when soft magnetic material is brought away from magnet
will lose magnetism
What happens when soft magnetic material is brought near a magnet
will become magnetised
Define magnetically soft (2)
magnets which do not stay magnetic
e.g electromagnets
Define magnetically hard (2)
stay magnetic once magnetised
e.g steel, iron
How does insulation maintain electricity safety (2)
prevents wires from touching each other
prevents people from touching wires
Electricity hazards (4)
long cables - trips/falls
water near sockets - water conductive –> connects person to mains supply (lethal)
pushing metal objects in sockets - connects person to mains supply
overloading sockets - too much current –> melt insulation and cause fire
Formula of energy in terms of electricity
energy (joules) = current (amperes) x potential difference (volts) x time (seconds)
Formula of power in terms of electricity
power (watts) = current (amps) x potential difference (volts)
Define transducer
device which transfers energy from one form to another
LDR resistance in light and dark (2)
high resistance in dark
low resistance in light
Function of light-dependent resistors (LDRs)
light sensors
Function of thermistors
temperature sensors
Function of variable resistor (2)
changes resistance
controls amount of current in resistor
What is the potential difference across a battery equal to in a series circuit
sum of potential difference across each lamp
Calculating combined resistance for parallel circuit
1/Rc = 1/R1 + 1/R2
Calculating combined resistance for series circuit (2)
Rc = R1 + R2
R1/R2 are resistors
Parallel circuit current equation
current from source = sum of current in branches of parallel
What is current measured using
ammeter
Disadvantage of parallel circuits
battery will not last as long
Advantage of parallel circuit (2)
light is brighter
if one lamp is broken circuit will still work
Disadvantages of series circuit
if one lamp is broken circuit is broken
Advantages of series circuit
battery last longer
Switches parallel circuit
other lamp will continue to work even if lamp is broken
Switches series circuit
lamps cannot be switched on/off independently
Battery of Parallel Circuit (2)
battery pushes charge along 2 different paths
more charge flows each second
Battery of Series Circuit (2)
must push same charge through one bulb
less charge flows each second
Lightbulb of parallel circuit
same brightness
Lightbulb of series circuit
lamps have same brightness
Current of parallel circuit
current splits with part of it going through each component
Current of series circuits
same electric current in each component in circuit
Why is resistance inversely proportional to cross-section area (3)
bigger area –> more electrons to carry charge along conductor –> lower resistance
Resistance relationship with cross-section area
inversely proportional
Why is resistance proportional to length (3)
longer conductor –> electrons must travel more –> more likely to collide with metal ions
Resistance relationship to length
proportional
Why does the rate of increase for current decrease to a certain extent as potential difference increases
temperature rise –> particles in conductor vibrate more and give more resistance to electron flow
Ohm’s law (2)
potential difference across component is directly proportional to current
resistance eventually becomes higher if temperature of conductor increases
resistance unit
ohms (omega sign)
potential difference unit
volts (V)
Resistance equation
resistance = potential difference / current
Where should you place a voltmeter
connected parallel across component being measured
How is potential difference/voltage measured
voltmeter
How is energy transferred in a circuit (2)
electrons given potential energy as they pass through power supply (battery)
transfer energy to circuit components as they move through a circuit
Define potential difference
energy that a unit of charge transfers between one point and another
Define electromotive force (2)
amount of energy to drive charge around a circuit
measured in volts
What is charge measured in
coulombs (C)
Current equation
current = charge/time (s)
Define current
amount of charge flowing per second
How do you measure current in an electrical circuit
ammeter
What is a current measured in
amperes/amps (A)
What charged particles is a current carried by
ions
Name of forces between opposite charges
electrostatic forces
Strength of electric field force factors (2)
closeness of particles - closer = larger force
amount of electrical charge - more charge = larger force
An electric field does not have a direction
True or False?
False
Define an electric field
a field around an object which the charges are not balanced
How is an electric current produced
electrons flow from one place to another
Define a static charge
unbalanced charge collected on the surface of an object
What happens when you charge an object with static electricity (2)
adding or taking away electrons
charge on object becomes unbalanced
Insulators or Conductors which are charged by being rubbed?
insulator
Best conductor
silver
Name a semi-conductor
silicon
Define insulators
substances that do not allow electric charge to pass through them
Define conductors
substances that allow electric charge to pass through them
