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physics ppe Flashcards

1
Q

what are the seven main stores of energy

A 
magnetic
internal (thermal)
chemical
kinetic
electrostatic
elastic potential
gravitational potential
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2
Q

what is magnetic energy

A

energy stored when repelling poles have been pushed closer together or when attracting poles further appart

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3
Q

what is internal (thermal) energy

A

total kinetic and potential energy of particles in an object

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4
Q

what is chemical energy

A

energy stored in chemical bonds

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5
Q

what is kinetic energy

A

energy of a moving object

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6
Q

what is electrostatic energy

A

energy when repelling charges moved closer and attracting charges further apart

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7
Q

what is elastic potential energy

A

energy stored when an object is stretched or squashed

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8
Q

what is gravitational potential energy

A

energy of an object at height

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9
Q

how long can energy remain in the same store

A

for millions of years or just a fraction of a second

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10
Q

when are energy transfers taking place

A

all the time

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11
Q

what happens when a system changes

A

change in the way some or all of energy is stored, can be transferred or dissipated

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12
Q

what are 4 examples of energy being transferred

A

mechanical work
electrical work
heating
radiation

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13
Q

what is the term for energy for being wasted

A

dissipation, spreads out into the surroundings

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14
Q

how is energy dissipated in a a mechanical system

A

when two surfaces rub together against friction

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15
Q

how to reduce dissipation in a mechanical system

A

use a lubricant

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16
Q

how to reduce dissipation in an electrical system

A

using energy-efficient components such as LED bulbs over filament lamps

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17
Q

how is energy usually lost

A

through heating up the surroundings

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18
Q

how can energy be sometimes dissipated

A

as sound waves

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19
Q

can energy be created or destroyed

A

no

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20
Q

what does energy come from and where is it transferred to

A

from one store to another

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21
Q

true or false: all the energy in the universe today was present at the Big Bang and will still be around until the end of time

A

true

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22
Q

how can a smartphone waste chemical energy

A

by converting it to internal energy through electrical work and releasing infrared radiation

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23
Q

what is the equation for kinetic energy

A

0.5 * mass * speed^2

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24
Q

what is the equation for elastic potential energy

A

0.5 * spring constant * extension^2

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25
Q

what is the equation for gravitational potential energy

A

mass * gravitational field strength * height

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26
Q

what is work done

A

energy transferred

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27
Q

what does the amount of work done depend on

A

the size of the force

the distance the force causes the body to move

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28
Q

what is the equation for work done

A

force * distance

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29
Q

what is the rate at which energy is transferred called

A

power

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30
Q

what is the equation for power (not electricity)

A

work done / time

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31
Q

what is the term for how good a device is at converting total energy to useful energy

A

effieciency

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32
Q

how are devices designed

A

to waste as little energy as possible

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33
Q

what is the equation for efficiency

A

useful energy transferred / total energy supplied

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34
Q

from where and to where can energy be transferred to or from

A

stores and place to place

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35
Q

how are the three ways energy moves

A

conduction
convection
radiation

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36
Q

how can conductivity of materials be compared

A

by examining the time taken to transmit energy through them

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37
Q

why is it better to have a window with two layers of glass and a layer of air trapped inbetween

A

because glass and air are both poor conductors as they have low thermal conductivities, the layer of air has the lowest and reduces the overall conductivity, they are also both transparent

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38
Q

materials needed for practical investigating methods of insulation

A
  • thermometer
  • stopwatch
  • piece of card
  • large beaker
  • small beaker
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39
Q

method for required practical investigating methods of insulation

A
  • put small beaker in large beaker
  • fill small beaker with hot water from kettle
  • put cardboard over beakers has lid, should have a hole
  • put thermometer through hole
  • record temperature in small beaker and start stop watch
  • record water temperature every 2 minutes
  • repeats steps with different insulating materials
  • plot graph temp (y axis) time (x axis)
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40
Q

what does graph show from practical investigating methods of insulation

A
  • shallowest curve is best insulator
  • temperature falls quickly at high temps and slowly at low temps
  • when beaker is heated, big difference between temp of beaker and temp of surrounding air, shows a high rate of transfer
  • when beaker is cooler, low difference between temp and surrounding air, shows a low rate of transfer
41
Q

hazards from practical investigating methods of insulation

A
  • boiling water can scald skin, do not overfill the kettle

- knocking beaker off desk can scald skin, do experiment whilst standing

42
Q

what happens when materials are heated

A

the molecules gain kinetic energy and start moving faster

43
Q

what is temperature a measure of

A

average kinetic energy of the molecules

44
Q

what does the amount of energy needed to heat an object depend on

A
  • the mass of the material
  • the substance of the material
  • desired temperature change
45
Q

what is the specific heat capacity of water

A

4,200 J/kg/degrees C

46
Q

what is the equation for working out change in thermal energy

A

change in thermal energy = mass * specific heat capacity * temperature change

47
Q

what are systems that can store large amounts of energy called

A

energy resources

48
Q

what are the major energy resources that can produce electricity

A
  • fossile fuels
  • nuclear fuel
  • bio-fuel
  • wind
  • hydroelectricity
  • geothermal
  • tidal
  • water waves
  • the Sun
49
Q

4 places energy is needed in

A
  • homes
  • public services
  • factories and farms
  • transport
50
Q

what are 2 dangers with fossile fuels

A
  • release CO2 causing global warming

- release Sulphur Dioxide which causes acid rain

51
Q

why does most of our electricity come from fossil fuels

A
  • existing infrastructure cheaper than new alternatives

- high power output

52
Q

advantage and disadvantage of nuclear fuel

A

-can release large amounts of energy compared to fossile fuels
-doesn’t emit CO2
but
-radioactive waste is difficult to store and dispose of

53
Q

factors that influence governments’ decisions about the use of energy resources

A

political and economic pressures

54
Q

what is a renewable energy resource

A

one that is being replenished as it is being used

55
Q

how can renewable resources be replenished

A
  • human action

- natural processes

56
Q

what is a non-renewable energy resource

A

a resource with a finite amount and will eventually run out

57
Q

why are fossil and nuclear power stations very reliable

A
  • provide most of country’s electricity

- operate almost continuously

58
Q

why is water power (tidal and hydroeletric) reliable and predictable

A

moon causes tides and rainfall fills reservoirs

59
Q

why are many renewable resources unreliable

A
  • cannot respond to increased demand
  • sunny and windy weather cannot be guaranteed
  • equipment used is expensive
60
Q

function of a thermistor

A

at low temps, thermistor has high resistance

at high temps, thermistor has low resistance

61
Q

function of a light-dependent resistor

A

low light levels, ldr has high resistance

at high light levels, ldr has low resistance

62
Q

function of diodes

A
  • allows current to flow one way only

- used to convert AC into DC

63
Q

what is the difference between AC and DC

A

in dc electrons flow consistently in one direction around circuit
in ac, direction of electron flow contrinually reverses

64
Q

what are electrons

A

negatively charged particles that transfer energy through wires as electricity

65
Q

what is electrical current

A

flow of electrons

66
Q

what is the equation for charge

A

current * time

67
Q

what is the equation for potential difference

A

energy / charge

68
Q

what is the equation for resistance

A

voltage / current

69
Q

why does the resistance of a filament bulb increase with energy inputted

A

the higher temperature increase vibrations of ions which makes it harder for electrons to get past

70
Q

how does electricity work in a series circuit

A

current is the same around the circuit
voltage splits but is added up
resistors connected in series are added up for total resistance

71
Q

how does electricity work in a parallel circuit

A

current splits but is added up
voltage is the same around the circuit
total resistance is reduced as current can take multiple paths

72
Q

what are the 2 equations for power electricity

A

current * potential difference

current^2 * resistance

73
Q

where are the 3 wires in a plug and what are their colours

A 
earth wire (green and yellow) top
neutral wire (blue) left
live wire (brown) right
74
Q

function of outer insulation

A

all three wires bundled together and extra plastic insulation for safety

75
Q

function of cable grip

A

holds the cable tightly so wires don’t become loose

76
Q

function of live wire

A

carries the current

77
Q

function of fuse

A

melts and breaks the circuit if the current gets too high

78
Q

function of neutral wire

A

connects cable to wall and completes circuit

79
Q

what would happen without an earth wire

A

live wire could touch the case and person who touches it could get electrocuted

80
Q

how does earth wire prevent danger

A

connects to case and metal pipe underground, in event of danger the current will pass through to the ground instead

81
Q

what is the equation for energy transferred

A

power * time

82
Q

what do step-up and step-down transformers do

A

increase voltage and decrease current

decrease voltage and increase current

83
Q

what is the function of a step-up transformer

A

to make sure that there is less heat is lost through the wire because of decreased current

84
Q

how are cables ensured that the minimum amount of power is lost

A
  • cables are thick so that their resistance is low

- high voltages reduece current through transmission lines

85
Q

what are charged atoms called

A

ions

86
Q

what happens when insulating materials rub each other

A

they become charged, the one that gains electrons becomes negative and the one that loses becomes positive

87
Q

what happens when cloth is rubbed on a polythene rod

A

polythene gains electrons

duster loses electrons

88
Q

what happens when cloth is rubbed on acetate

A

acetate loses electrons

duster gains electrons

89
Q

why do insulators create static electricity

A

they prevent the elctrons from moving and the charge remains, conductors cannot hold charge as electrons move through them

90
Q

what repels and attracts between positive and negative in an electrical field

A

positive charges move outwards

negative charges move inwards

91
Q

why would someone rubbing their feet on a carpet become shocked when touching a door handle

A

you become negatively charged so when you touch the positively charged door handle, the extra electrons will want to transfer from you to the handle

92
Q

why would an ammeter show a reading when a magnetic passes through a coil

A

the magnetic field around the magnet moves when the magnet does, the field lines cut through the coil which induces potential difference in the coil. A current is induced because the coil forms a complete circuit

93
Q

different properties of matter between states of matter

A

soilid - particles tightly packed in regular structure
liquid - tightly packed but free to move
gas - particles spread out move randomly

94
Q

what is the equation for density

A

mass / volume

95
Q

do the solid and liquid of the same element have a similar density

A

yes because the particles are tightly packed

96
Q

why would a gas have different density to the other two

A

because the same amount of mass is spread out in a wider area

97
Q

how can the volume of an irregular shape be measured

A

using a displacement can

98
Q

how does water displacement work

A

it is filled with water above a spout and is drained until water is level with bottom of spout, the volume of water in measuring cylinder is identical to the volume of object

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