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IGCSE Revision > Physics > Flashcards

Physics Flashcards

1
Q

What is the link between speed, distance, and time?

A

distance = speed x time.

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2
Q

How do you work out acceleration?

A

The change in velocity / time taken.

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3
Q

What does a flat, curved, and diagonal line mean on a distance time graph?

A

Stopped, accelerating or decelerating, and steady speed.

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4
Q

What does a flat, curved, and diagonal line mean on a velocity time graph?

A

Steady speed, increasing acceleration, and constant acceleration.

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5
Q

How do you work out distance on a velocity time graph?

A

The area.

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6
Q

What is gravity and what is weight?

A

Gravity is the force of attraction between all masses. Weight is the force with which gravity pulls any given object.

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7
Q

What are the units for weight and gravity.

A

Gravity is in N/Kg (how much force attracts a mass of 1Kg)

Weight is in N

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8
Q

What is the link between mass, weight, and gravity?

A

Weight = mass x gravity.

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9
Q

What happens to friction as speed increases?

A

It increases.

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10
Q

How could you investigate the motion of a toy car on a ramp?

A

Use light gates set apart equal distances and record with data-logging software.

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11
Q

What causes terminal velocity? What affects it?

A

As a falling object accelerates, the resistance increases. When the resistance force becomes equal to the weight pulling the object, the object will not be able to go any faster.
The weight, surface area, and aerodynamics.

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12
Q

Why do objects fall at the same speed?

A

Because even if they have different weights pulling them down, it takes inertia to move a bigger mass, which evens it out.

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13
Q

What happens when there are balanced and resultant forces?

A

A balanced force will either mean constant speed or no motion.
A resultant force will mean acceleration.

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14
Q

What is the link between force, mass, and acceleration?

A

Force = mass x acceleration

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15
Q

What is the difference between a scalar and a vector?

A

A scalar only has a size and a vector has a size and direction.

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16
Q

What 2 factors affect stopping distance and what affects these?

A

Thinking distance: speed, and dopiness.

Braking distance: mass, speed, conditions.

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17
Q

What is a moment and how do you work it out?

A

It is a turning effect of a force.

Moment (Nm) = force x perpendicular distance between the direction of the force and the pivot.(m)

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18
Q

What is the centre of gravity

A

It is the point through which the weight of a body acts.

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19
Q

How can you work out the centre of gravity of an irregular object?

A

Hang it and a plumb line from the same point. Make a mark, repeat. Look where the lines cross.

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20
Q

What is Hooke’s law?

A

It is that the extension of a wire or spring is directly proportional to the force pulling it.

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21
Q

What happens if you stretch a wire or spring far enough?

A

It will reach it’s limit to proportionality, and then it’s elastic limit so it won’t return to it’s original shape.

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22
Q

What are the different parts of the universe called?

A

The universe is everything in existence.
A galaxy is a collection of stars.
A solar system is a group of planets orbiting around the sun.

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23
Q

What causes orbits?

A

Objects have forwards motion, but also has the perpendicular force of gravity keeping it close to the planet/sun.

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24
Q

What is a comet and how does it orbit?

A

They are lumps of icy rock. They have elliptical orbits, and travel much faster when nearer to the sun because the increased pull of gravity makes it speed up.

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25
Q

How can you work out the speed of an orbiting object?

A

Orbital speed = 2 pi r / the time for one orbit

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26
Q

How should a plug be wired?

A
  • The neutral (blue) wire is on the left,
  • The green/yellow earth wire is in the middle,
  • The live brown wire is on the right with the fuse.
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27
Q

What is double insulation?

A

When an object is plastic coated with no metal parts showing. This means that no earth wire is needed.

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28
Q

What are some safety precautions for plugs?

A
  • Check it isn’t damaged.
  • Check there’s no water.
  • Turn the socket on and off
  • Don’t have too many plugs from one socket.
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29
Q

How does an earth wire work?

A

It stops you from getting a shock if there is a short circuit or accident, and an appliance becomes live. It provides a low resistance path for the electricity to flow to earth instead of through you.

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30
Q

What are the differences between fuses, circuit breakers, and RCCBs?

A
  • Fuses have a wire inside that melts if there is too much current.
  • Circuit breakers detect a surge in current and switch off, but can be reset with a press of a button.
  • RCCBs detect a difference in current between the live and the neutral wires and switch off.
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31
Q

What is a side effect of an electric current?

A

The wire gets hot.

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32
Q

How do you work out electrical power?

A

current x voltage (in watts)

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33
Q

How do you work out the transfer of electrical energy?

A

Current x voltage x time (s) (in joules)

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34
Q

Explain what current, voltage, and resistance are.

A

Current is the rate of flow of charge around a circuit.
Voltage is the driving force that pushes the current around.
Resistance is what causes the current to slow down when electrons bump into the ions.

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35
Q

What are the different parts of a wave diagram?

A
  • The height is the amplitude,
  • The frequency is the number of waves passed per second. (Hz)
  • The wavelength is the distance from one peak to the next. (λ)
  • The period is the time it takes for one wave to pass. (T)
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36
Q

How can you work out wave speed?

A

frequency (Hz) x wavelength (m) (in m/s)

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37
Q

What is the difference between a longitudinal and a transverse wave?

A
  • Transverse waves have vibrations perpendicular to the direction of energy transferred by the wave.
  • Longitudinal waves have vibrations in the same direction as the transfer of energy with compressions and decompressions.
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38
Q

What are the different types of electromagnetic waves? Which has the biggest wavelength? Highest frequency?

A

Radio waves (biggest wavelength), microwaves, infrared waves, visible light (Richard of York..), ultraviolet, x rays, gamma rays (highest frequency).

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39
Q

What are the properties of electromagnetic waves?

A
  • They can travel through a vacuum.
  • They travel at the speed of light.
  • They are transverse.
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40
Q

What are the nine types of energy and examples?

A 
Electrical - flowing current.
Light - the sun
Sound - music
Kinetic - anything in motion
Nuclear - released from nuclear reactions
Thermal - Hot things
Gravitational potential - Anything that can fall.
Elastic potential energy - springs
Chemical energy - batteries
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41
Q

What is the principle of the conservation of energy?

A

Energy cannot be created or destroyed, but only changed from one form to another.

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42
Q

How do you work out the efficiency of an appliance?

A

Useful energy output / total energy input

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43
Q

How does light reflect off a mirror?

A

When light bounces off a flat surface, the angle of incidence is equal to the angle of reflection (the angles coming out from the normal.

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44
Q

How do you draw a ray diagram and virtual image?

A

Place a light box on a piece of paper, and a mirror, and mark the beam(s) of light and the reflection(s).
Draw in the normal as a dotted line. Draw arrows to show the direction.
For the virtual image, continue the lines of reflection through the mirror until they meet.

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45
Q

How does sound travel in different mediums? What frequencies can we hear?

A

As longitudinal waves caused by vibrating objects. This causes the medium to compress and decompress. The denser the medium, the faster sound travels.
Between 20 and 20 000 Hz.

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46
Q

How do sound waves react to encountering different objects/ mediums?

A
  • They get reflected by hard flat surfaces.
  • Carpets will absorb sound.
  • Sound waves will refract and speed up when changing from air to water.
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47
Q

How can you measure the speed of sound in a lab?

A

Get two microphones and place them a set distance apart. Make a sound, and use data logging software to record and find out how long it took the sound to travel between the mics. S = D / T.

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48
Q

What does all energy eventually end up as?

A

Heat.

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49
Q

How do you draw a Sankey diagram?

A

Start off with the input energy. Divide the line into the different energy types in proportion to the amounts. Add all the information you know onto the arrows.

50
Q

How does conduction work?

A

The different particles vibrate and collide with each other, passing on the vibrations.

51
Q

How does convection and convection currents work?

A

More energetic particles move from a hotter region to a colder one, and bring their heat energy with them.
This can create a convection current, as hotter particles expand and are less dense, so rise, and cooler ones take their place.

52
Q

How does thermal radiation work?

A

It is the infrared electromagnetic waves that are absorbed and emitted by all objects. Black matt objects absorb and emit thermal radiation the best.

53
Q

What can you say about current and voltage in series? What are some of the advantages / disadvantages?

A

The current is the same everywhere, but the voltage is divided between components according to resistance.
Uses up less energy, but if one component breaks they all break.

54
Q

What can you say about current and voltage in parallel? What are some of the advantages / disadvantages?

A

The current is divided between circuits according to resistance, and the voltage is the same area.
The bulbs are brighter, and you have more control.

55
Q

How can you measure current and voltage in a circuit?

A

Ammeter can measure current in amps, and must be placed in series.
Voltmeters can measure the voltage when placed in parallel to a component.

56
Q

What is the difference between a.c and d.c

A

A.c constantly changes direction and is approx. 230 volts.

Direct current flows in the same direction.

57
Q

What is the link between current, resistance, and voltage?

A 
voltage = Current x resistance (ohms) 
V = I x R
58
Q

What do LEDs do?

A

They emit a light when a current flows through them in a forward direction. They are often used to show that an appliance is switched on.

59
Q

How do LDRs and Thermistors change with the environment?

A

More light will make a LDR less resistant.

More heat will make a thermistor less resistant

60
Q

How do you measure and calculate charge?

A

Charge is the amount of charge that passes a point every second.
Charge (coulombs C) = Current x time (s)

61
Q

What are some uses of radio waves and microwaves?

A

Radio waves are for communication.

Microwaves are used for satellite communication. They are also used for cooking as water absorbs the waves.

62
Q

What are the uses of infrared radiation and ultraviolet light?

A

Infrared radiation is used in heaters.

UV light is used in fluorescent lamps, where it is absorbed and then turned into visible light.

63
Q

How do optical fibres work and what is another use of visible light?

A

Optical fibres are made up of long tubes of fragments of glass, so that a beam of light travels inside it and will be totally internally reflected until it comes out the end.
Photography, where light is captured on film.

64
Q

What are X-Rays and gamma rays used for?

A

X rays let us see the internal structure of objects. The white bits on an Xray are where fewer rays get through.
Gamma rays kill bacteria, so can be used to sterilise equipment or food.

65
Q

How can 4 of the different EM waves be dangerous?

A
  • Microwaves can heat the body.
  • Infrared can cause heating and skin burns.
  • UV can damage and mutilate cells and cause blindness.
  • Gamma rays can cause cell mutilation, tissue damage, and cancer.
66
Q

What is refraction and how does it work?

A
  • It’s when light goes from one substance to another, and the speed and direction changes.
  • Light bends towards the normal if it slows down.
  • Light bends away from the normal if it speeds up.
67
Q

How would you show refraction with a rectangular glass block?

A
  • Shine a light ray through the glass at an angle. Mark where it enters and exits, and draw around the block. Remove the block and connect the entrance and exit points. Draw the normals.
68
Q

What is the critical angle? What is the formula for it?

A

The critical angle is the point just before there is total internal reflection. At the critical angle light is refracted close to 90 degrees.
Sin (critical angle) = 1 / n n is the refractive index

69
Q

What is an experiment for the critical angle?

A

Use a semicircular glass prism, and shine a ray of light at 90 degrees to the curved edge. Slowly move the ray around until it is totally internally reflected.

70
Q

What is snell’s law?

A

The refractive index, or how fast light travels in a substance is equal to sin(i) / sin(r)

71
Q

What is work and how can you work it out?

A

It is the energy transferred in moving an object in joules.

It equals to the force x the distance moved in the direction of the the force (m).

72
Q

What is power, and how can you work it out?

A

It is the rate of doing work in J / s or watts

It equals the amount of work done per second.

73
Q

How can you work out gravitational potential energy and convert that to kinetic energy?

A

GPE = mass (kg) x g x h (m)

The amount of kinetic energy that a falling object has is how much gravitational potential energy it has lost.

74
Q

How do you work out how much kinetic energy an object has?

A

0.5 x mass x velocity squared (m/s)

75
Q

What is a magnetic field, and what direction does it go?

A

It’s a region where magnetic materials experience a force. Field lines go from north to south.

76
Q

What happens to a magnetic field when two magnets are attracted to each other?

A

A uniform magnetic field is created, and the field lines are parallel.

77
Q

How can you look at a magnetic field?

A

Use a compass, and trace it’s path, or use iron filings.

78
Q

What happens when two magnets repel?

A

The magnetic fields are pushed back into the magnet, and there is a small zone with no magnetic field.

79
Q

Describe the magnetic field of a wire.

A

The field is made up of concentric circles, travelling according to the right hand grip rule.

80
Q

What does “soft” and “hard” mean in terms of magnetic materials?

A

Soft materials loose induced magnetism quickly.
Hard materials retain the magnetism permanently.
This is why soft iron cores are often used in electromagnets.

81
Q

What is the motor effect? How does the direction of the wire affect this?

A

It is that when you put a current carrying wire in a magnetic field, the wire will experience a force.
The full force occurs when the wire is perpendicular to the magnetic field. When it is parallel, there is no force.

82
Q

How can you work out the direction of the motor effect?

A

Left hand rule: thumb force, first finger field, second finger current.

83
Q

Describe a DC motor.

A

It is a coil of wire in between two magnets. It is connected to a split ring commutator. This is in contact with two brushes. This changes the direction of the current every half turn.

84
Q

How can you change the strength or direction of a motor?

A

Strength: current, magnet strength, turns on the coil, soft iron core.
Direction: current or polarity.

85
Q

How does a loudspeaker work?

A

A coil of wire inside a cylindrical magnet is connected to a cone. The change in direction of current changes the direction the coil moves in and out, vibrating the cone.

86
Q

What is electromagnetic induction?

A

The creation of voltage in a wire which is experiencing a change in magnetic field.

87
Q

How can you get a bigger voltage out of electromagnetic induction?

A

Increase the strength of the magnetic field.
Increase the number of turns on the coil.
Increase the speed of the movement.

88
Q

Describe an AC generator.

A

A coil of wire is rotated in a magnetic field, which is connected to two slip rings. These contact two brushes.

89
Q

How does changing the speed of a generator change the voltage?

A

High speed gets greater voltage, as well as faster change of voltage.

90
Q

What creates pressure in a gas?

A

The force of the particles bumping off the walls of the container.

91
Q

How does heating a gas create higher pressure?

A

The particles move faster with more kinetic energy, hitting the walls of the container more frequently and with more force, creating more pressure.

92
Q

What constant is there for a gas at a constant temperature?

A

pressure x volume = constant or p1v1 = p2v2.

93
Q

What is brownian motion and how does it support particle theory?

A

It is the movement of any particles in suspension. Pollen grains are being moved randomly by the water molecules.

94
Q

What important checkpoints are there for kelvin temperature.

A

Absolute 0 = 0K, 0 = 273K, 100 = 373K

95
Q

How do you work out density and what are the units?

A

p = mass / volume in g/cm3 or kg/m3

96
Q

How do you work out pressure? What are the units?

A

force / area, N/m2, or Pascals (Pa)

97
Q

How can you work out the pressure difference between two points in a liquid? What are the units?

A

pressure difference = height x density x gravity

(Pa) = (kg/m3) x (m) x g

98
Q

What are three ways of generating electricity from water ?

A
  • Tidal dams let the tide in and then close.
  • Dams in rivers let water in through turbines. The water can be pumped back up.
  • Costal wave converters use air forced up by waves against the shore to drive turbines.
99
Q

What are two non renewable energy sources?

A

Fossil fuels and nuclear energy.

100
Q

How do most power stations work?

A

They burn fossil fuels and use steam to drive turbines.

101
Q

How do nuclear reactors work?

A

Nuclear fission creates heat which makes steam which drives turbines.

102
Q

How does geothermal energy work?

A

Water is pumped down to hot rocks under the earth, which turns to steam, and turns a generator.

103
Q

What are isotopes?

A

They are atoms of the same atoms number (same element), that have different numbers of neutrons and different masses.

104
Q

What is radioactive decay?

A

It is when the nucleus of an unstable isotope breaks down randomly, emitting alpha, beta, or gamma radiation.

105
Q

What is background radiation, and where does it come from?

A

It is the radiation that is around all the time, from the air, food, rocks, the sun, and human activity. You must always remember when measuring radiation to measure background radiation first and then subtract it.

106
Q

What is ionisation?

A

Ionisation is when radiation particles or waves collide with atoms, and knock off electrons. This turns the atom into an ion. The further radiation can penetrate, the less ionising it is.

107
Q

What is alpha radiation?

A

It is a helium nucleus, made of two protons and two neutrons. They are heavy and slow moving, and are highly ionising so don’t penetrate far. They can be deflected by electric and magnetic fields.

108
Q

What is beta radiation?

A

It is when a neutron turns into a proton and an electron, and the electron is emitted from the nucleus. They move quite fast and are small, and are moderately penetrating and ionising. They can be deflected by electric and magnetic fields.

109
Q

How can you block the different types of radiation?

A
  • Paper and skin block alpha particles.
  • Thin metal stops beta particles.
  • Thick lead or concrete stop gamma rays.
110
Q

What were early theories of the atom like?

A

There was the plum pudding model, where atoms were spheres of positive charge, with tiny negative electrons stuck in them.

111
Q

What happened in Rutherford’s experiment?

A

Some of his students fired alpha particles at a sheet of gold foil, with alpha particle detectors surrounding it.

  • Most particles went straight through, because atoms are mostly empty space.
  • Some particles were deflected off at angles because they had passed near to a positive nucleus and been repelled.
  • Some particles were deflected right back because they at been repelled straight off the nuclei.
112
Q

How do you write a nuclear equation?

A

Write the starting atom with the mass over atomic numbers on the left. Draw an arrow and show the new atom + the type of radiation (both with mass and atomic numbers.)

113
Q

What is half life?

A

It is the time taken for half the radioactive atoms to decay.

114
Q

How can radiation be used as a medical tracer?

A

If someone swallows a beta or gamma source, the doctor can detect where it goes externally. This can be used to see if the organs are working properly. Only short half lives should be used.

115
Q

How can radiation be used as an industrial tracer?

A

You can put gamma sources into a pipe with a leak, so that you can detect a spike in radiation on the surface. It needs to have a short half life.

116
Q

How does carbon dating work?

A

You can compare the amount of carbon 14 in living things to the amount of carbon 14 in a sample, and work out how many half lives have passed. You can also compare the ratio of radioactive to stable isotopes in a sample.

117
Q

Why is radiation dangerous?

A

It can ionise the molecules in the cells of the body, which can cause a mutation. When a mutation divides uncontrollably, it is cancer.

118
Q

How does nuclear fission work?

A

U-235, when hit by a slow moving neutron, can split in two. It forms two new elements, and also releases a few more neutrons. These can trigger more fission, creating a chain reaction. In this process, a lot of energy is released.

119
Q

What happens in a nuclear reactor?

A
  • The uranium rods begin to react with some free neutrons.
  • A moderator (graphite or water), slows down the neutrons between the uranium rods.
  • Boron controll rods absorb neutrons and can be lowered to slow down the reaction.
  • A gas (e.g. CO2) absorbs the heat and is pumped away to heat some water.
120
Q

Why is it hard to dispose of radioactive waste?

A

Because it can stay radioactive for a very long time and needs to be buried in a safe place.

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