Physics Flashcards
(270 cards)
1
Q
Define conduction
A
transfer of thermal energy through a metal
2
Q
How does the motion of gas particles changes when they are cooled?
A
slow down
3
Q
Describe thermal conduction in a metal by electrons
A
electrons move freely throughout metal
4
Q
Difference between boiling and evaporation (2)
A
boiling occurs throughout liquid
evaporation occurs at surface only
5
Q
Technique to prevent energy loss from windows
A
double glazing - air between 2 panes of glass
6
Q
Technique to prevent energy loss from floors
A
carpet
7
Q
Technique to prevent energy loss from roof
A
loft insulation - insulation on top of ceiling prevents heat loss by conduction and convection
8
Q
Technique to prevent energy loss from walls
A
cavity wall - 2 single walls separated by air prevents conduction
9
Q
Does radiation need particles
A
no
10
Q
Define boyle’s law
A
when temperature of gas stays constant, volume of gas inversely proportional to pressure
11
Q
Define condensation
A
when substance changes from gas to liquid
12
Q
Define boiling point
A
temperature which substance changes from liquid to gas
13
Q
Define solidification
A
when substance changes from liquid to solid
14
Q
Define melting point
A
temperature which it changes from solid to liquid
15
Q
Factors that increase rate of evaporation (3)
A
higher temperatures
strong flow of air across surface
increased surface area
16
Q
Define evaporation
A
when particles break away from liquid surface and form a gas/vapour
17
Q
Define the brownian motion (2)
A
random motion of particles
large particles constantly hit by small fast particles
18
Q
Motion of gas particles (2)
A
random + fast motion
collide with other particles/walls
19
Q
Motion of liquid particles
A
slide over each other
20
Q
Motion of solid particles
A
vibrate in place
21
Q
Arrangement of gas particles (3)
A
irregular
widely spaced
particles able to move freely
22
Q
Arrangement of liquid particles (3)
A
irregular
closely packed together
particles able to slide over each other
23
Q
Arrangement of solid particles (3)
A
regular pattern
closely packed together
particles held in place
24
Q
Properties of gases (4)
A
assumes shape of container
assumes volume of container
can be compressed
flows easily
25
Properties of liquid (3)
assumes shape of container
is not easily compressible
flows easily
26
Properties of solids (4)
fixed volume
fixed shape
not easily compressible
does not flow easily
27
The hotter an object is the more infra red they emit. True or False?
true
28
What do all objects emit
infra red radiation
29
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
30
Why do metals conduct easier (2)
have free electrons
electrons can pass along metal allowing energy to transfer easily
31
Why are gases the worst conductors
their particles are far apart
32
Which state is the worst conductor of heat
gas
33
Why are solids the best conductors
their particles are close together
34
Which state is the best conductor of heat
solids
35
Define conduction (2)
method of heat transfer in solids, liquids, gas
transfers heat when vibrating particles bounce into each other
36
What increases the pressure of a gas (2)
increased temperature
decreased volume of sealed container
37
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
38
What happens when work is done on a gas (2)
increases internal energy
increases temperature of gas
39
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
40
What does an increase in temperature do to pressure
increases pressure
41
How does a car tire keep inflated (3)
gas particles collide with tire walls
pressure created (force over area)
pressure inflates tire
42
Pressure formula
force/area
43
Define range
difference between hottest and coldest that can be measured
44
Define sensitivity
smallest change that can be measured
45
Define linearity
if liquid expands by same amount for each temperature increase
46
Explain contraction of gases (2)
contracts once cooled
particles move back to original positions
47
Explain expansion of gases (2)
easier to expand as gas particles far apart
distance between particles increase when heated
48
Why do liquids contract when cooled
particles move less
49
Why do liquids expand when heated
particles move more and need more space
50
What liquids expand and contract in thermometers (2)
mercury
alcohol
51
What happens when a solid is cooled
gets smaller/contracts
52
What happens when a solid is heated
gets bigger/expands
53
How does sweat help to cool us down (2)
energy taken when water molecules evaporate
cools skin
54
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
55
What happens to atmospheric pressure as elevation above sea increases
decreases
56
What does an increase in energy cause for a system (2)
raises temperature
changes state
57
How does heating change the energy stored within a system
increases energy of particles
58
Define internal energy
energy stored in system
59
Are physical reactions easily reversible
yes
60
What is conserved when a substance changes state
mass
61
What increases as you go from solid to liquid (2)
volume
kinetic energy
62
Is nuclear energy renewable?
no
63
What energy do fossil fuels store
chemical energy
64
Examples of fossil fuels (3)
coal
oil
gas
65
Fossil fuels definition
carbon-based materials formed over millions of years from remains of plants and animals
66
cons of biomass energy
large area of land needed to grow trees
67
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
68
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
69
Cons of wind energy (2)
only works if windy
can be ugly and noisy
70
Pros of wind energy (3)
renewable
no pollution as nothing is burned
quite cheap and easy to build
71
Cons of solar energy (2)
solar cells and panels are expensive
only works if sunny
72
Pros of solar energy (2)
renewable
no pollution as nothing gets burned
73
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
74
Solar energy description
earth gets heat and light energy from sun
75
Cons of tidal energy (2)
costs money to build dam
dam can cause local flooding
76
Pros of tidal energy (3)
renewable
cheap to run
reliable since there are always 2 tides every day
77
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
78
Hydroelectric cons (3)
large area of land needed
damages wildlife habitats
dam can cause population displacement as it changes where water naturally flows
79
Hydroelectric pros (3)
renewable
no pollution - nothing gets burned
can store water and let water out when we need electricity
80
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
81
Pros of wave energy (2)
renewable
no pollution as nothing gets burned
82
Description of Wave energy (2)
sea waves have kinetic energy
machines bob up and down in waves generating electricity
83
Disadvantages of geothermal (2)
few places in the world to do this
cost money to drill into ground
84
Benefits of geothermal (3)
renewable
no pollution as nothing gets burned
doesn't damage environment
85
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
86
Can energy be created or destroyed?
no - only transferred
87
What is energy
ability to make something happen
88
Efficiency formula
(useful energy output/energy input) x 100
89
How does nuclear fission work
splitting nucleus releases stored energy
90
How does geothermal power work (3)
cold water pumped below ground
hot rocks heat water into steam
steam generates electricity
91
How does solar power work (2)
solar cells convert light energy to electrical energy
electric current charges battery that stores chemical potential energy
92
How does hydroelectric power work (4)
water flows through pipe to turbines
water turns turbine
turbine drives generator
generator produces electricity
93
How does wind power work (2)
kinetic energy of wind rotates blades
blades turn turbines that generate electricity
94
Define non-renewable
energy sources which cannot be replaced once used up
95
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
96
Where do we obtain most of our energy
fossil fuels (coal, oil gas)
97
Measurment of power
watts (W)
98
Power formula
work done (Joules)/time taken (s)
99
Define power
the rate of doing work/transferring energy
100
What is the law of conservation of mass
energy cannot be created or destroyed
101
Define sound energy (2)
transfer small amount of energy from the source of the noise
sound vibrates air particles as a longitudinal wave
102
Define light energy
light waves transfer energy to the object the light strikes (absorbed by)
103
Define electrical energy
electrical currents transfer electricity to different places
104
Define thermal energy
heat energy contained within an object
105
Define nuclear energy
energy stored between strong bonds of nucleus
106
Define chemical potential energy (2)
energy stored in atomic forces/bonds
energy can be transferred by breaking the bonds
107
Define elastic potential energy
energy stored in stretched objects
108
Define kinetic energy
energy stored by a moving object
109
Define gravitational potential energy
energy stored by an object raised up in a gravitational field
110
Formula for amount of kinetic energy stored
1/2 x mass (kg) x velocity^2 (m/s)
111
Formula for gravitational potential energy
mass (kg) x acceleration due to gravity (10) x height above ground (m)
112
Energy used to describe stored potential energy transferred to movement energy
kinetic energy
113
When a load is raised above the ground what energy will it gain
gravitational potential energy
114
When stretching or compressing a spring what energy will it have
elastic potential energy
115
Define potential energy
stored or hidden energy
116
When an object is lifted vertically, what does the amount of work done depend on? (2)
weight of the object
vertical distance it moves
117
When an object is lifted vertically, what is the force moved?
the weight of the object
118
Formula for work
work done = force x distance travelled in direction of force
119
Unit of work
joules (J)
120
What does the amount of work depend on (2)
magnitude of force
distance moved in the direction of force
121
What is work (2)
energy transferred
application of force which results in movement
122
Amplitude of sound wave
loudness of sound
123
Frequency of sound wave
pitch of sound wave
124
Range of human hearing
20Hz - 20,000 Hz
125
Uses of microwaves (2)
radar
cooking
126
Features of microwaves (2)
largest wavelengths
least amount of frequency/energy
127
Dangers of UV rays (2)
can damage surface cells of body
can cause blindness or skin cancer
128
Infrared radiation damage
can burn skin/body tissue
129
Speed which all electromagnetic waves travel in a vacuum
3 x 10^8
130
Features of infrared radiation (4)
emitted by all objects
hotter objects emit more than cold
3rd largest wavelength
4th greatest energy/frequency
131
Features of ultraviolet rays (3)
component of sun rays
3rd shortest wavelength
3rd greatest energy/frequency
132
Uses of X-rays (2)
treat cancer - destroy tumour cells
screen baggage/scan objects - different materials absorb different amounts of X-rays
133
Features of X-rays (3)
second greatest energy/frequency
second shortest wavelength
produced when high-energy electrons fired at target
134
Use of gamma rays (2)
radiotherapy - kill cancer cells
tracer - track substances in biological systems
135
Features of gamma rays (3)
shortest wavelength
greatest frequency/energy
can cause cancer/mutation in cells
136
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
137
Define the focal length
distance between lens and principal focus
138
Define the principal focus
point where parallel light rays all cross over
139
Features of convex(converging) lenses
cause parallel light rays to converge to one point
140
Define total internal reflection
at greater angles of incidence, rays entirely reflected back inside medium
141
Refractive index formula critical angle
1/sin(critical angle)
142
Define the critical angle
angle of incidence which angle of refraction becomes 90 degrees
143
Speed of light in vacuum
3 x 10^8
144
Refractive index of vacuu
1
145
Refractive index formula (2)
sin(angle of incidence) / sin (angle of refraction)
speed of light in vacuum (air) / speed of light in material
146
Define the refractive index
indicates
by how much a material changes direction of light
147
Define the angle of refraction
angle between refracted light ray and normal to surface
148
Define the angle of incidence
angle between incident light ray and normal to surface
149
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
150
Formula for angles of incidence/reflection
angle of incidence = angle of reflection measured to a normal when mirror reflects light
151
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
152
Define laterally inversion (2)
left and right exchanged
e.g in mirror
153
Features of light (2)
does not need medium to travel through
transverse
154
Define diffraction
when wavefronts change shape when they go through gap
155
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
156
Define refraction
wave enters new medium at angle = wavefronts change direction
157
Wave speed measurment
m/s
158
Formula for wave speed
frequency(Hz) x wavelength(m)
159
Define transverse wave
vibrations are at right angles to direction of wave travel
160
Amplitude of longitudinal wave
maximum displacement of medium's vibration from undisturbed position
161
Wavelength of longitudinal wave
distance between 2 consecutive points of maximum compression
162
Example of longitudinal waves
sound
163
Define compression
regions where wave is squashed together
164
Define rarefaction
regions where wave is spread out
165
Define longitudinal wave
vibrations in direction of wave travel
166
Define wavefront
moving line that joins all points on crest
167
Define amplitude (2)
height of half the crest/trough
maximum displacement of wave from undisturbed position
168
Define frequency
number of complete waves that go past each second
169
Define wavelength
distance between 2 adjacent peaks/troughs of wave
170
Define pressure (3)
how spread out a force is
ratio of force to area
force(N)/area (m^2)
171
Define stable equilibrium
object that is difficult to topple
172
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
173
When will an object fall
centre of mass outside pivot
174
Define centre of mass
one point where body mass all concentrated
175
Define the principle of moments (3)
if object not turning
sum of clockwise moments about pivot
= sum of anticlockwise moments about pivot
176
Define the turning effect of a force (2)
moment of the force
force (N) x perpendicular distance from pivot (m)
177
Define Newton's 3rd law
forces always come in pairs
178
Formula for force
mass (kg) x acceleration (m/s^2)
179
What will happen to the object if the forces are balanced (2)
object will be stationary
object will move at constant speed
180
Define newton's first law of motion
resultant force required to change the way something is moving
181
one form of friction
air resistance
182
Define friction
force between 2 surfaces which impedes motion and causes heating
183
Hooke's law formula
force (N) = spring constant (n/m) x extension of spring (m)
184
Define hooke's law
as force of weight increases = extension will proportionally increase until a certain limit
185
Define the limit of proportionality
point where extension no longer proportional to load
186
Effects of a force (3)
change object size
change object motion
change object shape
187
Define a force
push or pull
188
Density formula
mass (kg) / volume (m^3)
189
Earth gravitational field
10N/kg
190
weight measurement
newtons
191
Formula for weight
mass (kg) x gravitational field strength (N)
192
Distance from speed time graph
area under curve
193
graph for increasing acceleration
curved upwards exponential
194
Graph for steady acceleration
linear upward
195
Graph for steady speed
horizontal
196
Graph for acceleration
curved exponential upward
197
Graph for speed
linear upward sloping
198
Formula for acceleration (m/s^2)
change in velocity (m/s) / time taken (s)
199
Formula for speed (m/s)
distance (m)/time (s)
200
Circuit symbol for variable resistor
rectangle with arrow through
201
Circuit symbol for battery
-|I---|I-
202
Circuit symbol for fuse
rectangle with line through
203
Circuit symbol for Cell
-|I-
204
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
205
How do some modern alloys become magnetised (2)
magnetic field applied to molten alloy at high temp.
alloy solidifies while in magnetic field
206
How can a steel bar be magnetised (2)
stroking it with strong magnet
placing bar north and hammering it
207
How can permanent magnets become magnetized using electricity
large direct current running through coil of wire
208
Magnet will not continue to attract soft magnetic material even when material is turned around
True or False?
False
209
What happens when soft magnetic material is brought away from magnet
will lose magnetism
210
What happens when soft magnetic material is brought near a magnet
will become magnetised
211
Define magnetically soft (2)
magnets which do not stay magnetic
e.g electromagnets
212
Define magnetically hard (2)
stay magnetic once magnetised
e.g steel, iron
213
How does insulation maintain electricity safety (2)
prevents wires from touching each other
prevents people from touching wires
214
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
215
Formula of energy in terms of electricity
energy (joules) = current (amperes) x potential difference (volts) x time (seconds)
216
Formula of power in terms of electricity
power (watts) = current (amps) x potential difference (volts)
217
Define transducer
device which transfers energy from one form to another
218
LDR resistance in light and dark (2)
high resistance in dark
low resistance in light
219
Function of light-dependent resistors (LDRs)
light sensors
220
Function of thermistors
temperature sensors
221
Function of variable resistor (2)
changes resistance
controls amount of current in resistor
222
What is the potential difference across a battery equal to in a series circuit
sum of potential difference across each lamp
223
Calculating combined resistance for parallel circuit
1/Rc = 1/R1 + 1/R2
224
Calculating combined resistance for series circuit (2)
Rc = R1 + R2
R1/R2 are resistors
225
Parallel circuit current equation
current from source = sum of current in branches of parallel
226
What is current measured using
ammeter
227
Disadvantage of parallel circuits
battery will not last as long
228
Advantage of parallel circuit (2)
light is brighter
if one lamp is broken circuit will still work
229
Disadvantages of series circuit
if one lamp is broken circuit is broken
230
Advantages of series circuit
battery last longer
231
Switches parallel circuit
other lamp will continue to work even if lamp is broken
232
Switches series circuit
lamps cannot be switched on/off independently
233
Battery of Parallel Circuit (2)
battery pushes charge along 2 different paths
more charge flows each second
234
Battery of Series Circuit (2)
must push same charge through one bulb
less charge flows each second
235
Lightbulb of parallel circuit
same brightness
236
Lightbulb of series circuit
lamps have same brightness
237
Current of parallel circuit
current splits with part of it going through each component
238
Current of series circuits
same electric current in each component in circuit
239
Why is resistance inversely proportional to cross-section area (3)
bigger area --> more electrons to carry charge along conductor --> lower resistance
240
Resistance relationship with cross-section area
inversely proportional
241
Why is resistance proportional to length (3)
longer conductor --> electrons must travel more --> more likely to collide with metal ions
242
Resistance relationship to length
proportional
243
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
244
Ohm's law (2)
potential difference across component is directly proportional to current
resistance eventually becomes higher if temperature of conductor increases
245
resistance unit
ohms (omega sign)
246
potential difference unit
volts (V)
247
Resistance equation
resistance = potential difference / current
248
Where should you place a voltmeter
connected parallel across component being measured
249
How is potential difference/voltage measured
voltmeter
250
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
251
Define potential difference
energy that a unit of charge transfers between one point and another
252
Define electromotive force (2)
amount of energy to drive charge around a circuit
measured in volts
253
What is charge measured in
coulombs (C)
254
Current equation
current = charge/time (s)
255
Define current
amount of charge flowing per second
256
How do you measure current in an electrical circuit
ammeter
257
What is a current measured in
amperes/amps (A)
258
What charged particles is a current carried by
ions
259
Name of forces between opposite charges
electrostatic forces
260
Strength of electric field force factors (2)
closeness of particles - closer = larger force
amount of electrical charge - more charge = larger force
261
An electric field does not have a direction
True or False?
False
262
Define an electric field
a field around an object which the charges are not balanced
263
How is an electric current produced
electrons flow from one place to another
264
Define a static charge
unbalanced charge collected on the surface of an object
265
What happens when you charge an object with static electricity (2)
adding or taking away electrons
charge on object becomes unbalanced
266
Insulators or Conductors which are charged by being rubbed?
insulator
267
Best conductor
silver
268
Name a semi-conductor
silicon
269
Define insulators
substances that do not allow electric charge to pass through them
270
Define conductors
substances that allow electric charge to pass through them
