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Science > Physics Paper 2 > Flashcards

Physics Paper 2 Flashcards

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1
Q

what is a moment?

1 mark

A
  • forces cause objects to rotate
  • the turning force is called a moment
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1
Q

how do you work out a moment of force?

1 mark

A
  • force x distance
  • Nm = N x m
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2
Q

how would you get the max moment?

1 mark

A
  • push at right angles to maximes the distance
  • (normal to the direction of the force)
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3
Q

how do gears fit to transmit a turning effect?

3 marks

what direction? what makes it bigger?

A
  • their teeth interlock so if it turns the other will turn in the opposite direction
  • a force applied to a bigger moment will be larger as its further from the pivot
  • the larger the gear the slower it will spin
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4
Q

how do you work out how speeds and moments change?

3 marks

gears

A
  • gear ratio
  • if a gear has 10 teeth and another has 5 it will be 2:1
  • this means every 1 turn of the larger will turn the smaller one twice
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5
Q

why does resistance increase with temperature?

5 marks

A
  • work has to be done against resistance causing a electrical transfer of energy
  • some is put to thermal heating up resistor
  • this is because electrons colide with ions giving energy -> vibrate-> heat
  • the more vibrations the higher the resistance
  • however thermistors decrease resistance the higher the temperature
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6
Q

practical

how to use a circuit to investigate a filament lamp?

6 marks

also could be about a fixed resistor

A
  1. connect a series circuit (lamp,volt meter in parallel, ampmeter in series and a cell)
  2. change potential diffrence altering curent
  3. take readings of ampmeter and voltmeter to see how the current varies
  4. plot current against potential diffrence
  5. use data to work out resistance for each measurment to see the resistance changing
  6. make sure it doesnt get too hot and repeat for mean
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7
Q

how do you investigate a diode?

2 marks

A
  • take measurements with a range of currents
  • swap diodes direction and find that the current wont be able to flow
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8
Q

how can you investigate a Thermistors?

2 marks

heat dependant resistor

A
  • keep a constant potential difference and gradually heat thermistor
  • you should see as temp increases current through thermistor increases as the resistances decreases
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9
Q

how do you investigate LDRs?

3 marks

light depentant resistor

A
  • go in a dim room
  • keep potential difference constant and slowly adjust the light level near LDR
  • you should see as it gets brighter the current increases and resistance decreases
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10
Q

how does adding a resistor in parallel reduce total resistance?

3 marks

A
  • in parallel both resistors have the same potential difference
  • but by adding another loop the current has more than one direction to go in
  • this increases the total current that can flow decreasing the resistance
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11
Q

practical

how could you use a circuit to investigate properties

a long 4 marks :)

of resistor and filament lamp

A
  • vary the output potential difference and record reading (ammeter and voltmeter) from the series circuit
  • replace the resistor with a filament lamp and repeat
  • now connect a second filament lamp in parallel to the first and connect ammeters (1 in the second parallel and one by cell) and a second voltmeter with the second filament lamp
  • again vary potential difference and write down the current through each ammeter and p.d across each component

page 76 for the picture

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12
Q

what should you see when you investigate properties of circuits?

3 marks

of the resistor and filament lamp

A
  • for the series circuit as p.d increases the current through the resistor increases
  • similar but non-linear when using a filament lamp instead of a resistor
  • the same happens in a parallel but the overall current is higher and the resistance is lower
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13
Q

how do fuses protect circuits?

1 mark

A
  • they melt and break the circuit if the current gets too high
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14
Q

how is the heating of a circuit good?

3 marks

A
  • toasters contain a coil of wire with a high resistance that increases temp(so much it glows)
  • this gives off infrared radiation cooking the food
  • filament bulbs and electric heaters work the same way
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15
Q

what is the unit of power?

1 mark

A

watts

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16
Q

what is power?

1 mark

A

amount of energy transfered per second

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17
Q

what is a power rating used for?

3 marks

A
  • in microwaves the higher the power the faster it will take to cook
  • customers can see the lower the power the cheaper it is to run as it uses less electric
  • however its not always the case as it doesn’t show the efficiency
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18
Q

What does electrical power depend on?

2 marks

A
  • Current
  • Potential difference
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19
Q

What is a alternating current / whats it produced by?

4 marks

whats whe voltage and frequency of it in the mains

A
  • movement of charges that is constantly changing direction
  • prodused by Alternating voltages
  • Uk mains supply -> 230V
  • frequencey = 50Hz
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20
Q

what is direct current and hows it produced?

2 marks

A
  • produced by cells in direct voltage
  • one direction
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21
Q

what are the 3 separate wires in most cables?

3 marks

A
  • live wire
  • neutral wire
  • earth wire
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22
Q

what is the live wire?

2 marks

A
  • brown
  • carries the 230V
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23
Q

what is the neutral wire?

3 marks

A
  • blue
  • 0V
  • completes circuit
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24
Q

what is the earth wire?

4 marks

A
  • green and yellow
  • protects wiring
  • carries current away if it goes wrong
  • 0V
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25
Q

how do you get an electric shock?

4 marks

A
  • body is 0V
  • if you took live wire a large p.d produces a current through the body
  • this causes electric shock
  • even if the plug is off there is still a p.d even tho there is no current
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26
Q

what is a surge and what could it cause?

2 mark

A
  • sudden increase in current due to a change in a circuit
  • it can cause fires and electric shocks
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27
Q

how is a surge prevented?

4 marks

A
  • if live wire touches the metal case and the current gets too high the fuse will melt which breaks the circuit preventing shock and fire as it isolates the appliance
  • the fuse should be rated just above the normal current
  • the larger the current the thicker the cable as it stops it from getting too hot
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28
Q

what are circuit breakers?

4 marks

compared to a fuse

A
  • instead of a fuse a large current may turn off a circuit breaker
  • this is faster than a fuse melting
  • they can be reset so it’s easier than having to replace a fuse
  • more expensive than a fuse
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29
Q

what is double insulation?

3 marks

A
  • when there is no metal showing as it’s in a plastic coat
  • they only carry live and neutral wires (two-core cables)
  • they don’t need an earth wire
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30
Q

what is the build up of static caused by and how?

4 marks

A
  • when insulating materials are rubbed together
  • negatively charged ions will be scraped off one and dumped on the other
  • in insulators, electrons aren’t free to move
  • this build-up of charge is static electricity with positive static on the one that lost electrons and equal negative on the other insulator
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31
Q

how can electrically charged objects attract uncharged objects?

4 marks

A
  • charges on a surface can move a little
  • negative charges from a surface(like a balloon) repel the negative charges on another surface
  • this leaves positive charges to go to the front of the surface which will then attract the wall and balloon together
  • this is called attraction by induction
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32
Q

how can too much static cause a spark?

2 marks

A
  • potential difference between object and earth increases
  • when large enough electrons can jump across the gap between the object and the earth -> spark
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33
Q

what are 4 uses of electrostratic sprayers?

4 marks

A
  • Copying images on a photocopier
  • Reducing dust and smoke in industrial chimneys
  • Insecticide sprayers
  • Paint sprayers
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34
Q

How do paint sprayers work?

5 marks

A
  • Used on bikes and cars
  • Spray gun charges up small drops of paint
  • Each drop will repel as they have the same charge giving a fine spray
  • The object being painted is given an opposite charge to the gun to attract the paint
  • This gives an even paint without wasting
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35
Q

How does insecticide sprayers work?

4 marks

A
  • Used on crops
  • Spray charges up small drops
  • Each drop will repel as they have the same charge giving a fine spray
  • plants are charged by induction
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36
Q

how is refueling vehicles dangerous?

2 marks

in terms of static

A
  • Static can build up as fuel flows in
  • This can lead to a spark Which can cause an explosion in dusty or flumey places
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37
Q

what is the problem with static on planes and how does it occur?

2 marks

A
  • Friction between air and the plane causes it to become charged
  • This can interfere with communication equipment
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38
Q

how does lighting work?

3 marks

A
  • Raindrops and ice bump into each other inside storm clouds
  • Leaving the top of the cloud positive While the bottom is negative
  • This creates a huge voltage and a big spark, which can damage homes and start fires
39
Q

How can objects be earthed to stop electrostatic charge building up?

4 marks

A
  • Sparks can be prevented by connecting a charged object to the ground using a conductor (this is called earthing)
  • It provides an easy route for the Electrostatic charges to travel stopping build-up of charge
  • Electrons flow down if negative and up if positively charged
  • Fuel tankers must be earthed to prevent sparks leading to explosions
40
Q

what feild do you get when 2 oppositely charged parallel plates face?

1 mark

A

uniform field

41
Q

explain how can sparking be explained by electric feilds?

6 marks

A
  • When an object becomes statically charged it generates its own electric field
  • Sparks are caused when there’s a high enough potential difference between charged objects and the Earth.
  • Because this causes a strong electric field between the charged objects and the Earthed object.
  • strong feild causes electrons in the air to be removed
  • When air is ionised, it’s much more conductive, so a current can flow through it
  • making a spark
42
Q

what happends when you put a compass by a magnet and what does it allow you to do?

2 marks

A
  • it will line up with the magnetic field
  • this allows you to move the compass around and draw in the fields with the arrows
43
Q

what is an induced magnet?

2 marks

A
  • a temporary magnet
  • the magnet is only made when it’s in another field
44
Q

what is the relation between how quickly an object stop producing a feild and the maturial?

2 mark

A
  • the softer it is the faster(iron/nickel)
  • hard material is the slowest and the hardest ones and the permanent magnets
45
Q

explain what are all the uses of magnetic maturial?

7 marks

A
  • fridge doors -> permanent magnet to keep the fridge closed
  • cranes -> induced electromagnets to move magnetic material
  • doorbells -> Electomagnets turn on and off rapidly to release an arm that strikes a metal bell
  • magnetic separators -> separate metal items
  • maglev trains -> slightly float to reduce friction
  • MRI machines -> use magnetic fields to make images of the body without ionising radiation
  • speakers/microphones (page 90)
46
Q

how do you use you hand to work out direction that the field curves?

4 marks

A
  • right hand
  • thumb up which will be the direction of the current
  • close your fist so the direction that your fingers are pointing is direction of field
  • (anticlockwise or clockwise)
47
Q

how do you work out the dirction of motion (resulting force) of curent and a magenetic field?

5 marks

A
  • left hand
  • put your hand in position with each 90 degrees from the other
  • thumb -> motion
  • pointy finger -> direction field is going
  • middle -> current
48
Q

what is magentic flux density?

2 marks

A
  • how many field lines in a region
  • it shows strength of felid
49
Q

how does a coil of wire with a curent rotate in a magnetic feild?

3 marks

A
  • moter
  • forces act on 2 side arms of the coil of the wire carrying the current
  • these forces act in opposite directions so the coil rotates
50
Q

what does the spilt-ring commutator do to rotate a magnetic feild?

1 mark

A
  • it swaps the contact every half-turn to keep it rotating in the same direction
51
Q

how can the moter be reversed?

2 marks

A
  • swapping polarity of d.c. supply
  • or swapping magnetic poles
52
Q

what is a solenoid?

2 marks

A
  • a long coil of wire (loops)
  • electromagnet that can turn on and off using current

page 88

53
Q

how can you increase strength of magnetic felid?

made by a wire

A
  • wrapping it into a long coil of loops (solenoid)
54
Q

what happends when feild lines around each seperate loop of wire lines up?

5 marks

basically what does the feild look like in a solenoid

A
  • inside the solenoid, you get lots of field lines pointing in the same direction
  • the field is strong and almost uniform
  • outside the overlapping field lines cancel each other out
  • so at the ends of the solenoid they are weak
  • you end up with the same field lines as a bar magnet

p88

55
Q

how can you increase feild strengh of solonoid?

2 marks

A
  • increase curent
  • put iron in the center as it becomes and indused magnet
56
Q

what is electromagnet induction?

1 mark

A
  • the induction of potential difference (and current of its a complete circuit) in a wire which is experiencing a change in magnetic feild
57
Q

how can you get a electromagnetic induction through electrical conductors and magnetic feilds?

3 marks

A
  • Rotating a magnet or a coil of wire or a conductor In a magnetic field
  • If you rotate the magnet in opposite directions, then the potential difference and current will be reversed (likewise if you Reverse polarity)
  • If you keep a coil moving back and forth or keep rotating in the same direction, you will produce an alternating current.
58
Q

how can you increase the size of induced p.d?

3 marks

A
  • increasing the strength of the magnet
  • increase the speed of changing field
  • more turns per unit length on the coil
59
Q

how does induced current/p.d oppses the change it makes?

1 mark

A
  • using a magnetic field to return things to the way they were
60
Q

how do transformers work?

6 marks

A
  • using induction to change the size of the potential diffrence of an alternation current
  • two coils joined with an iron core
  • when alternating p.d is applied to primary coil it makes a alternating magnetic feild
  • iron core is magnetised and demagnetised
  • changing field induces a p.d on the second coil
  • this is almost 100% efficient
61
Q

what is the diffrence between a step-up and a step-down transformer?

4 marks

A

step up:
- increases p.d in the second coil
- more turns on the second coil
step down:
- decreases p.d
- less turns on secondary

62
Q

what is a dynamo?

2 marks

A
  • direct current generator
  • uses a split-ring communicator to swap connections every half turn to keep current flowing in the same direction
63
Q

what does a genorater do?

2 marks

A
  • applys a force to rotate a coil in a magnetic field
  • as the coil/magnet spins a current is induced in coil changing current every half turn
64
Q

how are alternators diffrent from dynamos?

2 marks

A
  • instead of a split ring they use a slip ring and brushes so the contacts dont swap every half-turn
  • this produces an alternating p.d and current if it forms a complete circuit
65
Q

how do microphones work?

6 marks

A
  • electromagnetic induction
  • sound waves hit a flexible diaphragm that is attached to coil
  • coil surrounds the pole of a permanent magnet and is surrounded by other pole
  • this means the diaphragm and coil move generating a current in coil
  • the movement of the coil depends on the properties of the wave
  • (the louder the further the diaphragm moves)
  • this is how microphones convert the pressure of vibrations into current
66
Q

how do loud speakers work?

3 marks

A
  • coil Is wrapped around one pole of a permanent magnet causing a force to move a cone
  • When the current is reversed, the force acts in the opposite direction
  • Movements make the cone vibrate, which makes the air around the cone vibrate making pressure that causes a sound wave.
67
Q

how do power stations use turbines to turn a huge alternator?

5 marks

A
  • fuels are burned to heat water converting it to steam - turning a turbine
  • turbine is connected to a magnet in a generator
  • as the turbine spins the magnet does as well inducing a large p.d and alternating current in coils
  • coils join in parrel to produce a single output
  • this is similar to hydroelectric, tidal and wind power but you dont have to heat anything to spin the turbine
68
Q

practical

how can you find the dencity of a object?

8 marks

A
  • measure mass using electronic balance
  • fill a bottle with a known Density liquid
  • place the stopper in the bottle
  • measure the mass of the bottle
  • empty the bottle and put the object in, then fill it back up before puting stopper back on
  • do the mass of the liquid - ( mass of liquid with object - mass of object) to get mass of displaced water
  • do that mass/density to get the volume of that object
  • mass of object/volume = density
68
Q

how would you find the dencity of a liquid?

4 marks

A
  • use an electronic balance to measure the mass of the measuring cylinder
  • pour liquid in and find the new mass to work out the change
  • find the volume of the liquid by looking at the scale
  • mass/volume = density
68
Q

how do transformers in the national grid work?

5 marks

A
  • after electric is generated it goes through a net of wires and transformers that conect power to the consumer(national grid)
  • it needs to transfer a large amount of power so it needs to have a high p.d or current
  • it can’t have a high current tho due to it heating up wire and losing efficiency
  • so they need high voltage and low resistance cables and transformers
  • step-up transformers are used (400,000V) to keep the current low then step-down transformers are used close to the consumer so make it safe
69
Q

how does specific heat capacity relate temperature and energy?

5 marks

A
  • heating increases thermal energy
  • this means the temperature is a way of measuring “internal energy”
  • but it takes more energy to increase the temp of some materials than others
  • materials that need to gain lots of energy to warm up also release loads when they cool
  • change in energy stored when you heat is related to the temperature by its specific heat capacity
70
Q

what is specific heat capacity?

1 mark

A
  • the change in energy in a substance thermal store needed to raise the temp of 1Kg of that substance by 1 degree
71
Q

practical

how can you find the specific heat capacity of water?

7 marks

A
  • use an electronic balance to measure the mass of the insulating container
  • fill the container with water and measure mass again to find the difference in masses which is the mass of water in the container
  • set up a joulemeter on 0 connecting it to an electric immersion heater in the container and put a lid on the container
  • measure temp of the water and then turn on the power
  • when it’s increased by 10 degrees stop the experiment and record energy on joulmeter and increase in temp
  • change in thermal energy / (mass x change in temp)
  • repeat for an average
72
Q

practical

how can you test to see that temp doesn’t decrease/increase(depending if you are melting or freezing) untill it changes state?

6 marks

A
  • fill a beaker with crushed ice
  • place the thermometer in and record temp of ice
  • using a Bunsen burner heat
  • at regular intervals record temp and state of ice
  • continue until it begins to boil
  • plot a graph of temp against time

p96 for graph

73
Q

what is specific latent heat?

1 mark

A
  • energy needed to change the state of 1Kg of that substance without changing the temp
74
Q

how are this diffrent?

  1. specific latent heat of fusion
  2. specific latent heat of vaporisation

2 marks

A
  1. between solids and liquids (melting/freezing)
  2. between liquids and gases (evaporating/condensing)
75
Q

what is kelvin?

2 maarks

A
  • negative 273 degrees
  • the coldest anything can be to where particles are basically still
76
Q

what happens when a container doesnt have a fixed volume?

2 marks

like a balloon

A
  • the volume becomes consistent where the pressure inside pushing out = pressure outside pushing in
  • you can change vol by changing the pressure on the inside or outside
77
Q

how can you change the pressure of a gas inside a container?

3 marks

A
  • heating/cooling
  • as e.g. a balloon is heated particles inside gain kinetic energy increasing pressure
  • then to outwards pressure would be higher than surrounding pressure causing the balloon to expand
  • cooling has the opposite effect
78
Q

how can you increase the external pressure on a gas?

3 marks

in an air tight syring and the atmosphere

A
  • push down on the plunger increases inward pressure so the inward pressure is larger than the outward
  • this causes compression
  • as you increase altitude the atmospheric pressure decreases rising container of gas as it expands due to a decrease in inward pressure
79
Q

what does doing work on a gas do?

1 mark

A

increases temp

80
Q

what does it mean for something to be (in)elastically distorted?

3 marks

A
  • inelastically distorted = object can’t go back to its original shape/length after a force was applied
  • when the object is stretched or compressed some energy is transferred to the elastic potential energy store
  • if that object is elastically distorted ALL energy is transferred to elastic potential
81
Q

what is elastic limit?

1 mark

A
  • the point at which an object stops distorting elastically and begins to distort inelastically
82
Q

what is extention directly proportional to?

2 marks

A
  • force
  • the constant depends on the material (the stiffer the bigger) :)
83
Q

when does extention stop being propotional to force?

1 mark

A
  • after the elastic limit when the object becomes permanently stretched
84
Q

how could you find what masses to uses when investigating the link between force and extention?

3 marks

A
  • pilot experiment
  • using an identical spring to the one you will be testing load it with masses one at a time and record the force and extension each time
  • plot a force-extension graph and check you get a straight line otherwise if its curved you will have to use lighter weights
85
Q

practical

how can you investigate the link between force and extention?

5 marks

A
  • measure the natural length of the spring (no load) with an mm ruler and add a marker to the top and bottom of the spring
  • add mass to the spring and allow spring to reset to the new length
  • the extension is the change in length
  • repeat process until you have enough measurements
  • plot a force-extension graph until it exceeds the limit of proportionality
86
Q

what should you see when you investigate the link between force and extention?

3 marks

A
  • The larger the force the larger the extension
  • force = gravitational force
  • area under linear part of graph = work done
87
Q

what is fluid pressure?

3 marks

A
  • pressure caused by collisions of gas/liquid on a surface
  • it always exerts force at right angles
  • depends on the area of fluid it is in contact with
88
Q

what does fluid pressure depend on?

1 mark

A
  • depth
  • density
  • gravitational field strengh
89
Q

describe how objects in fluids experience upthrust

4 marks

A
  • when an object is in a fluid the pressure of the fluid exerts a force in every direction
  • pressure increases with depth so the force at the bottom of the object is larger then the top
  • this causes a resultant force called upthrust
  • upthrust = weight of fluid displaced
90
Q

when do objects float and when do they sink?

5 marks

A
  • if upthrust = objects weight it will float otherwise it wont
  • this means it depends on the density
  • if an object is less dense than the fluid it displaces it will become equal to the upthurst so it will float
  • otherwise, it will sink as weight will always be large then upthrust
  • the less dense it is the higher up it will float
91
Q

what happens to atmospheric pressure when you go up and why?

3 marks

A
  • it decreases
  • on a graph, it is curved as pressure is affected by density which varies with height
  • as altitude increases there are fewer air molecules to collide with
92
Q

how is atmospheric pressure created?

1 marks

A
  • on a surface by air molecules colliding with the surface

Science (7 decks)

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