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BMAT > Physics > Flashcards

Physics Flashcards

1
Q

what is temperature the measure of ?

A

average KE of particles in a substance

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2
Q

0 kelvin is how many degrees Celsius ?

A

-273

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3
Q

what is heat measured as ?

A

Joules

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4
Q

what is heat a sum of ?

A

kinetic energy of all particles

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5
Q

what does increasing distance between particles do to the bonds?

A

decreases the strength

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6
Q

why does the temp of a substance not increase during melting/boiling ?

A

additional energy used to break intermolecular bonds

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7
Q

what is latent heat ?

A

the amount of energy needed to change the state of a substance

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8
Q

name the 4 factors of condensation

A

temp / surface temp / airflow / density

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9
Q

why is rate of condensation higher with greater density ?

A

particles closer - stronger forces

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10
Q

what is evaporation ?

A

liquid changing to a gas without boiling (average KE of particles is below BP)

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11
Q

individual particles only evaporate if …

A
  • high KE

- travelling towards surface

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12
Q

name the 4 factors of evaporation

A

temp / airflow / density / surface area

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13
Q

define conduction

A

process of vibrating particles passing on their KE to neighbouring particles in a material

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14
Q

why are metals good conductors ?

A

ions are tightly bound

free electrons can transfer energy

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15
Q

why are non-metals not very good at conducting ?

A

no free electrons

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16
Q

what is a fluid ?

A

substance with no fixed shape

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17
Q

what is convection ?

A

transport of heat energy through a fluid

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18
Q

why does hot air rise ?

A

less dense due to particles moving further apart from each other

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19
Q

what is the term for the cycle of hot air rising and cold air replacing it ?

A

convection currents

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20
Q

what is radiation (heat) ?

A

heat transfer from the emission of electromagnetic waves from warm bodies

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21
Q

why can radiation travel through space ?

A

does not require a medium

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22
Q

what is power the rate of ?

A

rate of energy change

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23
Q

power =

A

energy / time

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24
Q

what are the best absorbers and emitters of radiation ?

A

dark matte objects

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25
Q

what are the worst absorbers and emitters of radiation ?

A

bright and glossy objects

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26
Q

give the factors of heat transfer

A

SA / vol / material

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27
Q

list the features of a vacuum flask

A
  • vacuum between container and flask
  • inside and outside are shiny
  • insulating foam
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28
Q

why do warm climate animals have large ears ?

A

increases SA so can radiate more heat

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29
Q

density =

A

mass / volume

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30
Q

what is buoyancy dependent on ?

A

whether the object is more/less dense than the fluid

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31
Q

how to find volume of irregular solid?

A

place in beaker of water - find volume of displaced water

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32
Q

what is propagation direction ?

A

the direction a wave is travelling

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33
Q

define amplitude

A

maximum displacement of wave from resting position

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34
Q

define frequency of wave

A

no. of waves produced per second

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35
Q

1 Hz is ..

A

one wave per second

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36
Q

give 3 examples of transverse waves

A
  • electromagnetic waves
  • seismic S-waves
  • slinky up and down
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37
Q

in which direction do transverse waves vibrate ?

A

perpendicular to propagation direction

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38
Q

in which direction do waves vibrate ?

A

in propagation direction

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39
Q

give 3 examples of longitudinal waves

A
  • sound waves
  • seismic P-waves
  • slinky forward/backward
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40
Q

what are mechanical waves ?

A

require a medium to travel through

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41
Q

wave speed =

A

frequency x wave length

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42
Q

wave speed measured in …

A

m/s

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43
Q

time for single oscillation =

A

1 / frequency

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44
Q

what is the law of reflection ?

A

angle of incidence = angle of reflection

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45
Q

what is refraction ?

A

change in direction of a wave as it travels through a diff object with a diff refractive index

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46
Q

what causes refraction ?

A

diff refractive index causes increase/decrease in speed, causing to bend away/towards the normal

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47
Q

when will a wave not refract ?

A

at a right angle to surface

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48
Q

what is dispersion ?

A

refraction of light through a prism causing light to be split into diff colours

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49
Q

sound travels fastest …

A

in solids

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50
Q

what is pitch dependent on ?

A

frequency of the sound waves

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51
Q

ultrasound waves have a frequency of above …

A

20 000 Hz

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52
Q

infra sound waves have a frequency of below …

A

20 Hz

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53
Q

what is volume dependent on ?

A

amplitude of sound waves

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54
Q

what doe the EM wave lengths range from ?

A

10^-15m to 10^4m

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55
Q

at what speeds do EM waves travel through a vacuum ?

A

all travel at speed of light

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56
Q

what is speed of light ?

A

3 x 10^8 m/s

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57
Q

how are long radio waves able to travel long distances ?

A

long wavelengths can diffract

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58
Q

stopping distance =

A

thinking distance + braking distance

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59
Q

force =

A

mass x acceleration

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60
Q

what is static friction ?

A

between stationary object and surface

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61
Q

work done =

A

force x distance moved (in direction of force)

62
Q

what are the units for work done ?

A

joules

63
Q

work done is the same as …

A

energy transferred

64
Q

weight =

A

mass x gravitational field strength

65
Q

momentum =

A

mass x velocity

66
Q

what are the units for momentum ?

A

kg m/s

67
Q

force (momentum wise) =

A

change in momentum / time

68
Q

what are the two equations for Power =

A

work done / time

energy / time

69
Q

what is measured in watts ?

A

power

70
Q

what is a watt ?

A

one joule transferred in a second

71
Q

Kinetic energy =

A

0.5 x m x (velocity)^2

72
Q

when stopping a car…

KE transferred =

A

work done by breaks (Fd)

73
Q

Gravitational potential energy =

A

mass x g x height

74
Q

name the 9 different energies

A

kinetic, heat, light, gravitational, chemical, sound, electrical, elastic, nuclear

75
Q

efficiency =

A

useful energy output / total energy input

76
Q

how can wasted energy be reduced ?

A

heat exchanger used

77
Q

what is electric current ?

A

flow of charge

78
Q

potential difference (voltage) =

A

energy / charge

79
Q

what are the units for potential difference ?

A

volts

80
Q

what are the units for charge ?

A

coulombs

81
Q

charge =

A

current x time

82
Q

what are the units for current ?

A

amperes (amps)

83
Q

other potential difference (voltage) =

A

current x resistance

84
Q

what are the units for resistance ?

A

ohms

85
Q

what does a variable resistor do ?

A

alters current flowing through the circuit

86
Q

what device measures voltage ?

A

voltmeter

87
Q

what device measures current ?

A

ammeter

88
Q

for an ohmic conductor graph, what is the resistance ?

A

1 / gradient

89
Q

what is charging by friction ?

A

rubbing insulating materials and causing electrons to move

90
Q

when polythene is rubbed against a cloth duster, which way to electrons go ?

A

electrons move from duster to polythene

91
Q

how does static electricity help electronic paint sprayers ?

A
  • paint charged, droplets repel, fine spray

- surface of object is opposite charge, attracts, even coat

92
Q

what does cell do in a circuit ?

A 
supplies with power 
provides voltage (poten. diff.)  to move charge around circuit
93
Q

current =

A

voltage / resistance

94
Q

LED stands for …

A

light emitting diode

95
Q

LED emits light when …

A

current flows through it

96
Q

what do fixed resistor and variable resistor do ?

A

oppose flow of current, helping to set a value for current

97
Q

what does a thermistor do ?

A

changes resistance according to temp

98
Q

voltmeter is always placed in …

A

in parallel with components

99
Q

ammeter is always placed in …

A

in series with components

100
Q

what does a LDR do ?

A

changes resistance according to light shone on it

101
Q

what is a series circuit ?

A

components connected in a line

if there is a break, charge stops flowing

102
Q

describe the current in a series circuit

A

all the same throughout

A1 = A2 = A3

103
Q

describe the voltage in a series circuit

A

shared between components

Vtotal = V1 + V2…

104
Q

describe the resistance in a series circuit

A

shared between components

105
Q

what is a parallel circuit ?

A

components connected in loops, therefore if one is broken, charge is unlikely to stop flowing

106
Q

describe the current in a parallel circuit

A

shared between components

107
Q

describe the voltage in a parallel circuit

A

all the same throughout

108
Q

what is electromagnetic induction ?

A

production of a voltage across an electrical conductor in a changing magnetic field

109
Q

a voltage can be induced when :

A
  • magnet moved into coil of wire

- electrical conductor moved in a magnetic field

110
Q

direction of voltage or current can be reversed by :

A
  • changing direction of movement of conductor

- changing direction of magnetic field

111
Q

when is an alternating current (AC) produced ?

A

when magnet/coil moved backwards and forwards (keeps swapping direction of voltage)

112
Q

how can voltage be increased (4 ways)

A
  • move magnet faster
  • use stronger magnet
  • increase no. of turns in coil
  • increase coil area
113
Q

what is direct current (DC) and what is it produced by?

A

a battery produces this current, which is always in the same direction

114
Q

give order of flemmings left hand rule

A

force direction - magnetic field - current direction

115
Q

direction of magnetic field is …

A

north to south

116
Q

direction of current is …

A

positive to negative

117
Q

what is a step-up transformer and how does it work ?

A

changes a low-voltage supply to a high - increases voltage - more turns on secondary than primary coil

118
Q

what is a step-down transformer and how does it work ?

A

changes a high to low voltage - more turns on primary than secondary coil

119
Q

why is soft iron core used for transformers ?

A

easily magnetized, so transfers magnetic fields from primary to secondary coil

120
Q

describe how a transformer works (4 steps)

A
  • 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
Q

what do Vp and Vs mean ?

A

primary/secondary voltage

122
Q

what do Np and Ns mean ?

A

number of turns on primary/secondary coil

123
Q

give the ratio equation for transformer

A

Vp/Vs = Np/Ns

124
Q

how efficient are transformers and what does it mean ?

A

nearly 100% so

power in primary = power in secondary

125
Q

what power equation to use for ideal transformer equation ?

A

P = IV

126
Q

give the use for step-up transformers

A

produce high voltage for transmission of electricity to minimise energy loss by heat

127
Q

give the use for step-down transformers

A

reduces voltage to a safer value to be delivered to homes

128
Q

give the formula for power loss due to resistance in cables

A

P = I^2 x R

129
Q

what is the letter that represents charge ?

A

Q

130
Q

what is ionisation radiation ?

A

radiation that can cause other particles to lose electrons

131
Q

state the nature of alpha radiation

A

2 protons and 2 neutrons

132
Q

state the nature of beta radiation

A

an electron

133
Q

state the nature of gamma radiation

A

an EM wave

134
Q

state the charge of alpha radiation

A

+2

135
Q

state the charge of beta radiation

A

-1

136
Q

state the charge of gamma radiation

A

0

137
Q

state the ionising effect of alpha radiation

A

very strong (due to size)

138
Q

state the ionising effect of beta radiation

A

moderate

139
Q

state the ionising effect of gamma radiation

A

very weak (tends to pass through)

140
Q

state the penetrating effect of alpha radiation

A

slow moving so can be stopped by paper/skin

141
Q

state the penetrating effect of beta radiation

A

moderate, blocked by thin plate of metal

142
Q

state the penetrating effect of gamma radiation

A

high penetrating, blocked by thick metal plates

143
Q

give a use for alpha radiation

A

smoke alarms

144
Q

give a use for beta radiation

A

monitoring thickness of materials

145
Q

give 2 uses for gamma radiation

A

treat cancer

sterilise food / medical equipment

146
Q

what is fission the term for ?

A

splitting an atom into two smaller atoms

147
Q

what causes nuclear fission ?

A

slow moving neutron hitting into a large isotope

148
Q

what are the units for radioactive decay ?

A

Becquerel (Bq)

149
Q

what does 1 Bq represent ?

A

one nucleus decaying per second

150
Q

state the two factors of decay rate

A
  • the element

- how many undecayed nuclei in the sample

BMAT (4 decks)

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