Physics Flashcards
(150 cards)
1
Q
what is temperature the measure of ?
A
average KE of particles in a substance
2
Q
0 kelvin is how many degrees Celsius ?
A
-273
3
Q
what is heat measured as ?
A
Joules
4
Q
what is heat a sum of ?
A
kinetic energy of all particles
5
Q
what does increasing distance between particles do to the bonds?
A
decreases the strength
6
Q
why does the temp of a substance not increase during melting/boiling ?
A
additional energy used to break intermolecular bonds
7
Q
what is latent heat ?
A
the amount of energy needed to change the state of a substance
8
Q
name the 4 factors of condensation
A
temp / surface temp / airflow / density
9
Q
why is rate of condensation higher with greater density ?
A
particles closer - stronger forces
10
Q
what is evaporation ?
A
liquid changing to a gas without boiling (average KE of particles is below BP)
11
Q
individual particles only evaporate if …
A
- high KE
- travelling towards surface
12
Q
name the 4 factors of evaporation
A
temp / airflow / density / surface area
13
Q
define conduction
A
process of vibrating particles passing on their KE to neighbouring particles in a material
14
Q
why are metals good conductors ?
A
ions are tightly bound
free electrons can transfer energy
15
Q
why are non-metals not very good at conducting ?
A
no free electrons
16
Q
what is a fluid ?
A
substance with no fixed shape
17
Q
what is convection ?
A
transport of heat energy through a fluid
18
Q
why does hot air rise ?
A
less dense due to particles moving further apart from each other
19
Q
what is the term for the cycle of hot air rising and cold air replacing it ?
A
convection currents
20
Q
what is radiation (heat) ?
A
heat transfer from the emission of electromagnetic waves from warm bodies
21
Q
why can radiation travel through space ?
A
does not require a medium
22
Q
what is power the rate of ?
A
rate of energy change
23
Q
power =
A
energy / time
24
Q
what are the best absorbers and emitters of radiation ?
A
dark matte objects
25
what are the worst absorbers and emitters of radiation ?
bright and glossy objects
26
give the factors of heat transfer
SA / vol / material
27
list the features of a vacuum flask
- vacuum between container and flask
- inside and outside are shiny
- insulating foam
28
why do warm climate animals have large ears ?
increases SA so can radiate more heat
29
density =
mass / volume
30
what is buoyancy dependent on ?
whether the object is more/less dense than the fluid
31
how to find volume of irregular solid?
place in beaker of water - find volume of displaced water
32
what is propagation direction ?
the direction a wave is travelling
33
define amplitude
maximum displacement of wave from resting position
34
define frequency of wave
no. of waves produced per second
35
1 Hz is ..
one wave per second
36
give 3 examples of transverse waves
- electromagnetic waves
- seismic S-waves
- slinky up and down
37
in which direction do transverse waves vibrate ?
perpendicular to propagation direction
38
in which direction do waves vibrate ?
in propagation direction
39
give 3 examples of longitudinal waves
- sound waves
- seismic P-waves
- slinky forward/backward
40
what are mechanical waves ?
require a medium to travel through
41
wave speed =
frequency x wave length
42
wave speed measured in ...
m/s
43
time for single oscillation =
1 / frequency
44
what is the law of reflection ?
angle of incidence = angle of reflection
45
what is refraction ?
change in direction of a wave as it travels through a diff object with a diff refractive index
46
what causes refraction ?
diff refractive index causes increase/decrease in speed, causing to bend away/towards the normal
47
when will a wave not refract ?
at a right angle to surface
48
what is dispersion ?
refraction of light through a prism causing light to be split into diff colours
49
sound travels fastest ...
in solids
50
what is pitch dependent on ?
frequency of the sound waves
51
ultrasound waves have a frequency of above ...
20 000 Hz
52
infra sound waves have a frequency of below ...
20 Hz
53
what is volume dependent on ?
amplitude of sound waves
54
what doe the EM wave lengths range from ?
10^-15m to 10^4m
55
at what speeds do EM waves travel through a vacuum ?
all travel at speed of light
56
what is speed of light ?
3 x 10^8 m/s
57
how are long radio waves able to travel long distances ?
long wavelengths can diffract
58
stopping distance =
thinking distance + braking distance
59
force =
mass x acceleration
60
what is static friction ?
between stationary object and surface
61
work done =
force x distance moved (in direction of force)
62
what are the units for work done ?
joules
63
work done is the same as ...
energy transferred
64
weight =
mass x gravitational field strength
65
momentum =
mass x velocity
66
what are the units for momentum ?
kg m/s
67
force (momentum wise) =
change in momentum / time
68
what are the two equations for Power =
work done / time
| energy / time
69
what is measured in watts ?
power
70
what is a watt ?
one joule transferred in a second
71
Kinetic energy =
0.5 x m x (velocity)^2
72
when stopping a car...
| KE transferred =
work done by breaks (Fd)
73
Gravitational potential energy =
mass x g x height
74
name the 9 different energies
kinetic, heat, light, gravitational, chemical, sound, electrical, elastic, nuclear
75
efficiency =
useful energy output / total energy input
76
how can wasted energy be reduced ?
heat exchanger used
77
what is electric current ?
flow of charge
78
potential difference (voltage) =
energy / charge
79
what are the units for potential difference ?
volts
80
what are the units for charge ?
coulombs
81
charge =
current x time
82
what are the units for current ?
amperes (amps)
83
other potential difference (voltage) =
current x resistance
84
what are the units for resistance ?
ohms
85
what does a variable resistor do ?
alters current flowing through the circuit
86
what device measures voltage ?
voltmeter
87
what device measures current ?
ammeter
88
for an ohmic conductor graph, what is the resistance ?
1 / gradient
89
what is charging by friction ?
rubbing insulating materials and causing electrons to move
90
when polythene is rubbed against a cloth duster, which way to electrons go ?
electrons move from duster to polythene
91
how does static electricity help electronic paint sprayers ?
- paint charged, droplets repel, fine spray
| - surface of object is opposite charge, attracts, even coat
92
what does cell do in a circuit ?
```
supplies with power
provides voltage (poten. diff.) to move charge around circuit
```
93
current =
voltage / resistance
94
LED stands for ...
light emitting diode
95
LED emits light when ...
current flows through it
96
what do fixed resistor and variable resistor do ?
oppose flow of current, helping to set a value for current
97
what does a thermistor do ?
changes resistance according to temp
98
voltmeter is always placed in ...
in parallel with components
99
ammeter is always placed in ...
in series with components
100
what does a LDR do ?
changes resistance according to light shone on it
101
what is a series circuit ?
components connected in a line
| if there is a break, charge stops flowing
102
describe the current in a series circuit
all the same throughout
| A1 = A2 = A3
103
describe the voltage in a series circuit
shared between components
| Vtotal = V1 + V2...
104
describe the resistance in a series circuit
shared between components
105
what is a parallel circuit ?
components connected in loops, therefore if one is broken, charge is unlikely to stop flowing
106
describe the current in a parallel circuit
shared between components
107
describe the voltage in a parallel circuit
all the same throughout
108
what is electromagnetic induction ?
production of a voltage across an electrical conductor in a changing magnetic field
109
a voltage can be induced when :
- magnet moved into coil of wire
| - electrical conductor moved in a magnetic field
110
direction of voltage or current can be reversed by :
- changing direction of movement of conductor
| - changing direction of magnetic field
111
when is an alternating current (AC) produced ?
when magnet/coil moved backwards and forwards (keeps swapping direction of voltage)
112
how can voltage be increased (4 ways)
- move magnet faster
- use stronger magnet
- increase no. of turns in coil
- increase coil area
113
what is direct current (DC) and what is it produced by?
a battery produces this current, which is always in the same direction
114
give order of flemmings left hand rule
force direction - magnetic field - current direction
115
direction of magnetic field is ...
north to south
116
direction of current is ...
positive to negative
117
what is a step-up transformer and how does it work ?
changes a low-voltage supply to a high - increases voltage - more turns on secondary than primary coil
118
what is a step-down transformer and how does it work ?
changes a high to low voltage - more turns on primary than secondary coil
119
why is soft iron core used for transformers ?
easily magnetized, so transfers magnetic fields from primary to secondary coil
120
describe how a transformer works (4 steps)
- primary coil connected to AC supply
- changing current produced changing magnetic field in primary
- induces an alternating voltage in secondary through iron core
- induces AC in secondary
121
what do Vp and Vs mean ?
primary/secondary voltage
122
what do Np and Ns mean ?
number of turns on primary/secondary coil
123
give the ratio equation for transformer
Vp/Vs = Np/Ns
124
how efficient are transformers and what does it mean ?
nearly 100% so
| power in primary = power in secondary
125
what power equation to use for ideal transformer equation ?
P = IV
126
give the use for step-up transformers
produce high voltage for transmission of electricity to minimise energy loss by heat
127
give the use for step-down transformers
reduces voltage to a safer value to be delivered to homes
128
give the formula for power loss due to resistance in cables
P = I^2 x R
129
what is the letter that represents charge ?
Q
130
what is ionisation radiation ?
radiation that can cause other particles to lose electrons
131
state the nature of alpha radiation
2 protons and 2 neutrons
132
state the nature of beta radiation
an electron
133
state the nature of gamma radiation
an EM wave
134
state the charge of alpha radiation
+2
135
state the charge of beta radiation
-1
136
state the charge of gamma radiation
0
137
state the ionising effect of alpha radiation
very strong (due to size)
138
state the ionising effect of beta radiation
moderate
139
state the ionising effect of gamma radiation
very weak (tends to pass through)
140
state the penetrating effect of alpha radiation
slow moving so can be stopped by paper/skin
141
state the penetrating effect of beta radiation
moderate, blocked by thin plate of metal
142
state the penetrating effect of gamma radiation
high penetrating, blocked by thick metal plates
143
give a use for alpha radiation
smoke alarms
144
give a use for beta radiation
monitoring thickness of materials
145
give 2 uses for gamma radiation
treat cancer
| sterilise food / medical equipment
146
what is fission the term for ?
splitting an atom into two smaller atoms
147
what causes nuclear fission ?
slow moving neutron hitting into a large isotope
148
what are the units for radioactive decay ?
Becquerel (Bq)
149
what does 1 Bq represent ?
one nucleus decaying per second
150
state the two factors of decay rate
- the element
| - how many undecayed nuclei in the sample
