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🌌 > Wrong Questions - P1 to P4 > Flashcards

Wrong Questions - P1 to P4 Flashcards

1
Q

What happens when work is done on a gas?

A
  • gas is compressed
  • force is needed to move the gas particles together
  • work is done on the gas
  • the gas gains ke and moves faster
  • temp of gas increases as temp is the avg ke of particles
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2
Q

What happens when work is done by a gas?

A
  • gas expands
  • force applied by particles
  • work done by gas
  • lose ke
  • move slower
  • temp decreases
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3
Q

What is free fall?

A
  • movement of a body through a drag producing medium without a drag producing device
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4
Q

When will a body float?

A
  • if enough upthrust before fully submerging And displaces enough fluid =to its weight
  • if more surface area, then a small depth is needed to displace water volume equal to its weight
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5
Q

How does an electric motor work?

A
  • electric motor has wires in a mag field
  • wire experiences force due to LHR and F = BIL
  • current flows and thus creates a rotational force around a pivot point
  • after halfway = parallel but moves due to its own momentum
  • split ring commutator keeps motor turning in the same direction as it reverses current every half turn (brushes reconnect every half turn)
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6
Q

What is ozone?

A
  • it absorbs most damaging UV light
  • UV radiation and oxygen is needed to make the ozone layer
  • if there is high CO2 or low o2 in a planet = probably has no ozone layer
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7
Q

Why is the temperature of Venus more than the Earth ?

A

More photons hit Venus than earth

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8
Q

What happens when a person jumps on the trampoline?

A
  • energy is transferred from the trampoline to the person
  • gpe to ke as she falls down, then ke to epe (elastic potential energy) to ke as she jumps up, then gpe as she goes back up
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9
Q

How can you figure out a average speed without calculations?

A
  • gradient

- steep = faster

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10
Q

How could half lives of isotopes be billions of years but also seconds?

A
  • half lives are vary widely between different isotopes
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11
Q

How does wearing helmets affect people?

A
  • helmet reduces the force or absorbing energy
  • like a crumple zone
  • increases the time of collision while having the same momentum
  • rate of change of momentum decreases
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12
Q

If another identical bulb is added to a parallel circuit embedded in a series circuit, what happens to the voltage and current?

A
  • the voltage stays the same as the p.d in each loop is the same and there is the same no of cells
  • the current increases as the overall resistance of the circuit decreases as there are more pathways for electrons to travel
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13
Q

What’s the issue with a high activity?

A
  • will be hot

- needs storing underwater or in containers

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14
Q

Units of momentum

A

N/s or kgm/s

- this is as 1N = 1kgm/s^2 so divide both by s, which is 1N/s = 1kgm/s

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15
Q

What colour loses the least energy?

A
  • silver loses the least energy as less heat would be radiated out and thus lost
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16
Q

Why would the spring constant be higher than the actual value?

A
  • friction and air resistance were ignored but they were acting on the object
  • so the energy in the object’s ke store is lower than the energy transferred by the spring in stretching as some of the ke is actually lost
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17
Q

What is momentum not conserved?

A
  • when an external force acts on the object
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18
Q

What are interaction pairs?

A
  • forces that act on different objects
  • forces are the same size and type
  • forces act in opposite directions
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19
Q

What is 1J equal to?

A
  • Joules is the measure of energy
  • energy transferred is work done, which is force times distance
  • Force is in Newtons and Distance is in M so 1J= 1Nm
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20
Q

What is the principle of moments?

A
  • total clockwise moment = total anticlockwise moment

- if they are balanced

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21
Q

How can force be calculated?

A
  • f = ma

- f = change in momentum over time

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22
Q

How can acceleration be calculated?

A
  • acceleration = (2*distance)/time
  • change in velocity/ time = acc
  • fv^2 - iv^2 = 2as
  • distance = (initial velocitytime) + (0.5acc*time squared) - s=(ut)+(0.5at^2)
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23
Q

How does the momentum affect force?

A
  • a faster change in momentum means a larger force is experienced by the object
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24
Q

Where does energy transfer to when springs are stretched?

A
  • to the elastic potential energy
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25
Q

Why don’t elastic bands have a linear extension at the start?

A
  • they have very low elastic limits
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26
Q

How can energy transferred in spring be calculated on a graph?

A
  • energy transferred in stretching the spring (can only be found until the elastic limit)
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27
Q

How can moments be compared between two gears?

A
  • force between two gears is the same

- moment changes between two gears

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28
Q

What is the mechanical advantage?

A

= load/ effort

  • more than one?
  • effort = what you put in
  • if the load is closer to pivot = smaller momentum but a larger overall force so less effort needs to be put in
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29
Q

What is moment?

A
  • turning effect of a force
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30
Q

What should you do when cycling uphill or accelerating in terms of gears?

A
  • low gear as it needs a large mechanical advantage
  • smaller Gear [input] to the Larger Gear [output]
  • moment increases as more perpendicular distance* force
  • 2nd gear turns more slowly
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31
Q

What should you do when cycling fast or on level ground in terms of gears?

A
  • high gear
  • larger Gear [input] to the Smaller Gear [output]
  • the moment decreases as force and less perpendicular distance
  • 2nd gear turns more quickly
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32
Q

What is Newton’s Third Law?

A
  • when 2 bodies interact, the two forces are the same in size​ but act in opposite directions.​
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33
Q

Examples of where the rule of conservation of momentum applies?

A
  • firing a gun

- rocket moving

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34
Q

How do seatbelts protect people?

A
  • (the user will experience a) large change in momentum when a collision occurs
  • seat belt increases the time for this to occur or
    the seat belt stops you from hitting something which would stop you quickly
  • the seatbelt decreases the rate of change of momentum and thus the force on the user is less
  • less chance of (serious/fatal) injury
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35
Q

How do crumple zones work?

A
  • time of collision increases
  • so a smaller force is exerted (NOT absorbs energy or momentum)
  • to produce the same change of momentum or impulse force
36
Q

How does charge build up on a Van de Graaff generator’s dome?

A
  • belt brushes past the positively charged comb at the bottom
  • electrons in the belt are attracted towards it
  • belt is not positively charged
  • belt brushed past second comb attached to the dome
  • electrons in second comb are attracted towards belt and transferred off it
  • second comb and thus the dome and now positively charged
  • as belt continues going around = more charge builds up on dome
37
Q

What happens to the sealed glass of air when it is heated?

A
  • mass and density of gas stays the same
  • volume stays the same
  • speed of molecules and pressure exerted by the gas decreases
38
Q

Which way around do you put a diode?

A
  • the base of the triangle should link to the positive terminal (longer line)
  • tip of the triangle line should link to the negative terminal (shorter line)
39
Q

Why is a potential difference induced in a battery

A
  • positive terminal has more electrical potential than the negative terminal
40
Q

What is the graph for a diode like?

A
  • very high resistance in the negative area

- current in one direction so reversing current means 0 A and infinity resistance

41
Q

How does resistance change in a thermistor?

A
  • made of semiconducting material - silicon
  • electrons don’t need much energy to escape from the current
  • when electrons escape, it creates a current
  • more temperature means more energy for electrons to escape, more delocalised elections, thus less resistance and more current
  • more temp = less resistance
42
Q

How does resistance change in an LDR?

A
  • more light intensity = less resistance

- light causes electrons to be released in a circuit

43
Q

Using field lines, explain why negative charges repel:

A
  • There is an electric field around all charged objects.
  • The field can be represented by field lines, which try to straighten.
  • When you bring two negatively charged objects together the field lines are distorted
  • So the charges move apart (repel) to straighten the field lines.
44
Q

Why does a thundercloud have 2 regions of charge?

A
  • Before the cloud was charged it was neutral so there must be two regions of charge in the cloud, one positive and one negative.
45
Q

Why does pepper grain form a field?

A
  • Electrons in the pepper grain move away from the positive rod and towards the negative rod.
  • There is a field around the pepper grain because one end is negative and one end is positive.
  • This distorts the field, so the pepper grains line up so that the field lines are as straight as possible
46
Q

Define potential difference:

A
  • Potential difference = A difference in (electrical) potential produced by the separation of charge that enable charges to do work, the energy (work
    done) by a charge.
47
Q

Why does a wire glow?

A
  • The wire contains a lattice of positive ions. As the electrons move through the wire they collide with the ions and transfer energy.
  • The ions vibrate more and the wire gets hotter and glows.
48
Q

When is a thermistor or LDR more sensitive, at higher or lower temperatures/ light intensity?

A
  • It would be more sensitive at low temperatures.

- At low temperatures, a small change in temperature produces a large change in resistance.

49
Q

Why does a lamp’s brightness not change when it is in a parallel circuit with an LDR?

A
  • voltage across lamp does not change as p.d in each loop is the same
  • thus current in lamp does not change = same brightness
50
Q

Why may radio waves be produced by transmission lines?

A
  • Alternating currents/(electrical/electron/particle)
    oscillations produce (radio) waves/electromagnetic
    radiation
51
Q

How do gliders use force to decrease their height?

A
  • less thrust from engine means that there is lower air resistance
  • less momentum/ ke
  • the force of lift is less than height = lands on ground
52
Q

Explain what happens when a person jumps off a plane and then opens a parachute?

A
  • Speed increases so drag increases
  • resultant force reduces so acceleration is reduced
  • Drag force approaches the weight until weight = drag and she moves at a terminal velocity
  • after the parachute opens = Speed decreases as drag > weight
  • A larger resultant force gives a high deceleration to reach terminal velocity
  • larger surface area (from the parachute) gives
    drag=weight at a lower speed than before
53
Q

Explain why lorries need a larger brake pad than cars?

A

The lorry has more KE than a car at the same velocity (1)
More absorption of energy by larger brake discs (1)
Higher rate of dissipation of energy to surrounding air (1)
Brakes less likely to overheat (1)

54
Q

Describe how a sensing circuit works:

A
  • dark = light intensity decreases and resistance increases as electrons have enough energy to escape atoms
  • atoms are already vibrating
  • LDR resistance is more than the fixed resistor resistance
  • LDR has a greater share of p.d. compared to a fixed resistor
  • light in the parallel circuit has the same p.d.
  • p.d is high enough for light tot turn on/ become brighter
55
Q

Describe how resistance in a filament lamp change?

A
  • current flows = electrons collide with the vibrating ions
  • transfer energy to the ions = higher temp as the temp is the measure of avg ke of a particle
  • ions vibrate faster
  • even more electrons collide and less pass by
  • less current and more resistance
  • slope/ gradient changes with p.d. IF VI graph
56
Q

How do you know if the magnetic field strength is stronger?

A
  • stronger at the poles
  • field lines are closer together
  • DONT TOUCH FIELD LINES
57
Q

Why does pressure change with depth?

A
  • pressure is heightgfsdensity

- pressure is due to the weight above the water due to the force of gravity

58
Q

How can naturally occurring rocks be magnetic?

A
  • The naturally occurring rock contain iron

- The iron is magnetised by the magnetic field of the Earth

59
Q

What is a solenoid?

A

A solenoid is a coil of wire, sometimes with a core that is usually made of a magnetic material.

60
Q

Why should the number of turns be rounded down in the secondary coil?

A
  • if you round it up, the p.d. may be bigger than expected and damage the appliance.
61
Q

What happens when the input coil of a transformer is in a circuit that is connected to a battery supply that is dc?

A
  • needle moves to left / right when switch of circuit is closed
  • needle moves opposite way when the switch is opened
  • returns to zero after the switch is closed/opened
  • needs a.c. for p.d. to be induced constanly
62
Q

Why is alternating current needed in transformers?

A
  • AC produces a changing magnetic field
  • a changing magnetic field produces a changing
    voltage / current in the coil so it can be stepped up to down
  • a d.c. doesn’t produce a alt magnetic field
63
Q

How can you change the speed of a motor?

A
  • variable resistor

- changing the p.d or current

64
Q

How does the speed of a motor change when it’s not continually turned on and off?

A
  • smoother speed / less jerky

- variation in motor speed will be less

65
Q

In an electromagnet, what controls its strength?

A
  • no of coils
  • magnitude of current
  • type of core - iron core?
66
Q

How is an alternating magnetic field produced from an alternating current?

A
  • an alternating circular magnetic field grows around the wire
67
Q

What is a catapult field?

A
  • current in a wire creates a circular magnetic field which creates a third catapult field (motor effect)
  • creates a stretched field in which there are more lines either above or below the wire
  • to straighten and shorten the field lines, the wire experiences a force
68
Q

How does a motor work?

A
  • current flows in different directions on each side of the coil
  • wires attached to axle or spindle
  • wires between 2 poles of a magnet
  • each coil side is perpendicular to the pole of the magnet ( when parallel it experiences no force )
  • thus experiences a force in different directions making it spin
  • to keep spinning a split-ring commutator is made
69
Q

Why is an iron core used?

A
  • iron is magnetic so guides the magnetic field

- no current flows in the iron core due to the coils

70
Q

What happens when you push a magnet towards a coil?

A

current in coil generates a magnetic field 

which opposes the change causing it / is a like pole

71
Q

What is Lenz law

A

the direction of the induced current is in such a direction that it opposes the change that caused it
- keeps magnetic flux constant as energy is conserved

72
Q

What is the minimum number of circles should you draw to show current?

A

3

73
Q

Why does a motor keep rotating continuously?

A
  • the current creates a magnetic field
  • the sides of the coil (parallel to the magnet) experience a force (in opposite directions) due to FLHR
  • the forces cause moments that act in the same (clockwise / anticlockwise) direction = coil rotates
  • the magnetic fields interact, causing the coil to rotate - the two halves of the (rotating) commutator swap from one (carbon) brush to the other
  • the commutator reverses the current (in the coil) and thus keeps the current in the same direction relative to the (permanent) magnetic field
74
Q

How can the potential difference induced be maximised in the generator effect?

A
  • increase the speed of coil/ rotation speed
  • strengthen the magnetic field of magnets
    β€’increase area of the coil - more turns
75
Q

What is the difference between the output of an alternator and a dynamo?

A

the alternator pd changes polarity, the 2ndtype of generator does no

76
Q

At which part of the national grid is a step-up transformer used?

A
  • after the power station
  • after the generator
  • before the power lines
  • before the pylons
77
Q

Why are the wires in a transformer insulated?

A
  • to prevent short-circuiting
  • ensure that the current flows / goes round the coil
  • to prevent the current entering the core
78
Q

What does a laminated transformer mean?

A

constructed in (thin) layers

79
Q

Why are transmission lines so high up?

A
  • (several metres of) air gives good electrical insulation (between cables and earth) o
  • reduce the chance of earthing or sparks
  • to avoid people touching it
80
Q

How does a loudspeaker work?

A
  • the current in the electrical circuit is alternating
  • the alternating current passes through the coil
  • alt current produces an alt magnetic field in the coil of wire
  • alt mf of coil interacts with one of permanent magnet
  • the coil experiences a force (inwards or outwards) through FLHR
  • reversing the current reverses the direction of force
  • the size of the current affects the size of the force
  • the alternating current causes the coil to vibrate
  • the (vibrating) coil causes the cone to vibrate
  • the vibrating cone causes the air molecules to move
  • the movement of the air molecules produces the pressure variations in the air needed for sound waves
  • the air molecules bunch together forming compressions and spread apart forming rarefactions
81
Q

How do transformers work?

A
  • alt p.d in P coil = a.c in P coil
  • a.c in P coil = alt mf in P coil
  • alt mf in P coil induces alt mf in soft iron core as easily magnetised and it guides the alt mf to the S coil
  • alt. mf in core induces alt p.d in S coil
  • if S coil part of circuit = alt p.d in S coil = a.c in S coil
82
Q

What happens when you move a north-facing permanent magnet through a solenoid?

A
  • mf of magnet cuts the coil of the solenoid
  • induces a pd in the coil = if closed circuit then current produced = m.f produced in solenoid
  • current direction is opposite to the change that caused it
  • so top of solenoid is N so it repels the magnet
  • when magnet is leaving the coil, the bottom turns North pole to repel the magnet
  • reaches terminal velocity as force produced is opposite and equal to the one by magnet
83
Q

How can you slow down a falling lift if the cable breaks?

A
  • The lift is fitted with permanent magnets and made to travel inside a metal tunnel (which means it can be magnetised)
  • If the cable breaks, the lift will fall due to the force of gravity, and the magnets will move past the metal surfaces of the tunnel.
  • The metal surfaces will cut magnetic field lines, inducing a p.d. and current in them as it’s a loop and thus a closed circuit
  • due to Lenz Law the direction of induced current opposes the change that caused it ​
  • The current-carrying surface of the lift shaft will now interact with the magnetic field of the magnets, giving rise to a motor force.​ - FLHR and mf interacting = force
  • This motor force will act upwards, opposing the motion of the lift, causing it to fall/accelerate at a lesser rate (than it would under the force of just its weight)
  • thus magnetic flux is constant = terminal velocity reached = falls slowly
84
Q

What happens when a magnet approaches a coil of wire?

A
  • If a magnet approaches a coil of wire with its north pole, the p.d. induced (current) in the coil of wire will give rise to a north pole on the end the magnet is approaching.​
  • The north pole of the magnet and the north pole of the coil will then repel by Lenz Law ​, opposing the motion inducing the p.d.
85
Q

How do you know an image is virtual?

A
  • cannot be formed on a screen

- rays of light seem to come from it but do not pass through it

86
Q

What type of wave is used to send information to and from satellites?

A
  • microwaves as they can pass through the ionosphere
87
Q

Why should the iron core of a transformer have no gaps? And why is an iron core hot?

A
  • no gaps = mf transferred from primary to secondary coil efficiently
  • thus no power loss in 2nd coil
  • iron core has currents with high resistance
  • thus energy is transferred to the surroundings as heat

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