Sunday, 25 August 2013


Unfortunately I am not going to be taking physics A-level, and as much as I'd love to carry on all three of my science blogs, only biology will survive!

For anyone who is interested- or who I couldn't reply to before now- I got an A* in GCSE Edexcell Physics (bio A*, chem A*.) Everything I knew for the exam is on the blog :) Obviously the spec will change, making it less and less helpful each year :( but I'll leave it up as the information will hopefully still be helpful.

Corrections and questions are still welcome as I don't want to have incorrect information up- so will still be making minor changes.

Thank you for all the lovely comments, best of luck with physics,

Wednesday, 8 May 2013


So I have now finished covering all of the specification for physics! Very exciting!
Hopefully people will makes use of this, whilst also remembering that I may have made mistakes (please feel free to correct me.)

Good luck to everyone!

If I make any resources I may share them...
In the mean time here are some of the resources that I have used when making my notes:

5.5 understand that the pressure at a point in a gas or liquid which is at rest acts equally in all directions

If you have a gas or liquid, it will be exerting an equal pressure in all directions.

4.17 describe the advantages and disadvantages of methods of largescale electricity production from various renewable and nonrenewable resources.

Fossil fuels: non renewable; release CO2.

Burning wood: renewable; release CO2; destroy habitats.

Wind power: visual pollution; produces small amounts of electricity for space and effort in comparison to other methods.

HEP: expensive to set up; limited places to put it; can kill fish.

Solar cells: rely on the weather.

Nuclear power: dangerous; many waste products.

There are many more types of power and fors/againsts but these are a few important ones.

1.26 recall that the weight of a body acts through its centre of gravity

An objects centre of gravity is where all of its weight acts through.

7.20 understand the role played by the control rods and moderator when the fission process is used as an energy source to generate electricity.

In nuclear power stations, nuclei are split by having neutrons fired at them, these release other neutrons as well as a large amount of energy. The energy is used to create electricity, and the radioactive by-products are disposed of.

Control rods can absorb neutrons. If there are two many neutrons the chain reaction could get out of control, so the control rods are lowered in to the reaction to absorb some neutrons and control the reaction.

The moderator slows neutrons down so that they are at the right speed to split nuclei, the moderator is usually water.

7.19 understand that a chain reaction can be set up if the neutrons produced by one fission strike other U-235 nuclei

When split by a neutron, uranium-235 releases neutrons (as well as splitting in half.) These neutrons can then go on to hit other U-235 nuclei which then do the same thing, this will be repeated in a chain reaction.

7.18 understand that the fission of U-235 produces two daughter nuclei and a small number of neutrons

When a neutron is fired at a uranium-235 nucleus, it splits in two. This leaves two 'daughter' nuclei.

At the same time, neutrons are emitted.

7.17 understand that a nucleus of U-235 can be split (the process of fission) by collision with a neutron, and that this process releases energy in the form of kinetic energy of the fission products

Uranium-235 has a large nucleus that can be split in two when a neutron is fired at it. This releases a large amount of energy as the products created move rapidly.

7.16 describe Rutherford’s nuclear model of the atom and how it accounts for the results of Geiger and Marsden’s experiment and understand the factors (charge and speed) which affect the deflection of alpha particles by a nucleus

The nuclear model of an atom is the one we all know: a central nucleus with positive protons and neutral neutrons surrounded by orbiting negative electrons.

Before the Geiger Marsden experiment, the 'plum pudding' model of an atom was believed: a positive sphere contained negative electrons dotted inside. If this was true the alpha particles would have gone straight through the sheet of gold and all come out the other side.

What actually happened was that some were deflected at different angles, this showed that the positive alpha particles were being repelled by a positive charge and others were going through the space between the charged areas. The faster they hit it the faster they were repelled. This is where the idea was formed of a nucleus and orbiting electrons.

7.15 describe the results of Geiger and Marsden’s experiments with gold foil and alpha particles

Alpha radiation was beamed at a sheet of gold foil, a sheet of zinc sulphide surrounding the foil showed where the alpha particles ended up; a few went straight through, many were deflected at angles, some were deflected straight back.

Tuesday, 7 May 2013

7.14 describe the dangers of ionising radiations and describe how the associated risks can be reduced.

Radiation can cause mutations in living organisms: radiation can damdge the stucture of a cells DNA, when the cell replicates the changes (mutation) will be passed on; this can be how cancer is caused.

Radiation can damage cells and tissue: atoms can be change by radiation, this prohibits them functioning properly, this can mean cells and so tissue are damaged.

The problems arising in the disposal of radioactive waste: this waste emits radiation that, as shown above, can be dangerous. If the waste is put into water it can poison ecosystems, similarly with land. Radioactive waste tends to be buried under the ground; with the thinking that when it is much less harmful it can be dug up and disposed of.

7.13 describe the uses of radioactivity in medical and non-medical tracers, in radiotherapy, and in the radioactive dating of archaeological specimens and rocks

Tracers- a radioactive source is put into a system (like a piping network), it will build up where there is a blockage a be detected, showing where a problem is.

Medical tracers- a radioactive source is put into a body and will build up at a blockage so an area of problem can be detected.

Radiotherapy- radiation is used to destroy unwanted cells (cancerous cells.)

Radioactive dating- aka carbon dating. The amount of radiation from an object is measured, the half life of the carbon is then used to see how old the object is. Archaeologists use this to tell the age of an object.

7.12 use the concept of half-life to carry out simple calculations on activity

Some people use equations to work out half life calculations, but you don't really need to. Make sure that you understand that half life is the time taken for the amount of radiation emitted to half; two half lives is the amount of time taken for the value to half twice (ect.)

The papers often contain half life graphs to interpret. Draw a line from half the value of the start point to the curve, draw down to the bottom line and you will get your half life. If you are doing this in an exam the mark scheme sometimes requires that you make it clear you were halfing the start number.. odd but there we go.

7.11 understand the term ‘half-life’ and understand that it is different for different radioactive isotopes

A half-life is the time it takes for the radiation emitted by a source to decrease by half.
Half-lives are different for different sources of radiation.

7.10 understand that the activity of a radioactive source decreases over a period of time and is measured in becquerels

The radiation emitted by a radioactive source will decrease over time. Radiation is measured in becquerels.

7.9 explain the sources of background radiation

There are so many sources of background radiation: different radioactive materials are in the environment.
An example of this is boron in the soil which emits radiation; cosmic rays from space are radioactive too.

50% radon gas from the ground, 12%  buildings and the ground, 12% food and drink, 12% cosmic rays, 14% artificial sources - mainly cosmic rays, small amount of nuclear power and weapons test

7.8 understand that ionising radiations can be detected using a photographic film or a Geiger-Muller detector

Radiation imprints on camera film.

A Geiger-Muller detector (or GM counter) beeps in the presence, the more radiation the more frequent the beeps.

7.7 understand how to complete balanced nuclear equations

Nuclear equations show the atoms atomic number and atomic mass on one side and the radiation (with mass and number) and the new element (with mass and number.)

For example, uranium has experienced alpha decay:


Here lithium has experienced beta decay:

7.6 describe the effects on the atomic and mass numbers of a nucleus of the emission of each of the three main types of radiation

Alpha makes an atom go down 2 on its atomic number and four on its atomic mass: it will change to the element with a the atomic number 2 less than it was.

When beta radiation occurs a neutron splits into a proton and a electron, the electron is emitted from the atom, but the proton stays in the nucleus: this changes the atomic number up one, the element becomes that with the next atomic number up. The mass number remains the same as a neutron- mass 1- became a proton- mass 1.

Gamma rays have no specific effect on the atomic or mass number.

7.5 describe the nature of alpha and beta particles and gamma rays and recall that they may be distinguished in terms of penetrating power

alpha particles are two neutrons and two protons; also known as a helium nucleus. Alpha particles could not penetrate a piece of paper if they tried.

Beta particles are electrons, they are emitted when a neutron turns into a proton and an electron. It won't penetrate aluminium.

Gamma rays are a type of electromagnetic wave, they are often emitted alongside the other types of radiation. Gamma cannot penetrate lead.

7.4 understand that alpha and beta particles and gamma rays are ionising radiations emitted from unstable nuclei in a random process

alpha particles, beta particles and gamma rays are all types of radiation.
The term ionising means they damage cells.
Radiation is emitted from the nucleus of an atom that is unstable (in a way it is too full and trying to off load.)

7.2 describe the structure of an atom in terms of protons, neutrons and electrons and use symbols such as 14C 6 to describe particular nuclei

Protons (+) and neutrons are in the nucleus of an element. Electrons (-) orbit on shells (or orbitals.)

7.3 understand the terms atomic (proton) number, mass (nucleon) number and isotope

The atomic mass of an element (the number written above an elements symbol) is the number of protons + the number of neutrons.

The atomic number is the number of protons. This will equal the number of electrons in an element.

An isotope of an element is one with the same configuration of protons and electrons but a different amount of neutrons.


7.1 use the following units: becquerel (Bq), centimetre (cm), hour (h), minute (min), second (s)

becquerel (Bq) (measure of reactivity)
centimetre (cm)
hour (h)
minute (min)
second (s)

6.20 know and use the relationship: input power = output power

input power = output power
(primary voltage x primary current = secondary voltage x secondary current)

This is only true if we assume that something is 100% efficient and has lost no energy in other forms (like heat)

6.19 know and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer

primary voltage/ secondary voltage = primary turns/ secondary turns

Vp/Vs = Np/Ns

6.18 explain the use of step-up and step-down transformers in the largescale generation and transmission of electrical energy

In the national grid (the system which delivers electricity around the country) transformers are used. Because the wires are long there is more resistance, so a high current will cause a lot of heat; which is dangerous and looses a lot of energy. When electricity leaves a power plant, a step up transformer is used, this means the voltage is high, but the current is low. When electricity reaches a home or business it is stepped down to make it useful in appliances that we use, the wires are shorter so less of a danger is presented by this.


6.17 describe the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides

A transformer is used to change the current and voltage of electricity.

A current carrying wire is wrapped round one side of a transformer, another wire is wrapped round the other. There will be the same amount of power on both sides, but one will have a higher voltage and lower current the other a lower voltage and a higher current.

The transformer is made of iron, this is because it is a soft metal and can be turned on and off as a magnet: the current from the first wire induces a magnetic field in the transformer, this then induces a current in the second wire.

More coils causes more higher voltage (and lower current.) So if the second side has more turns of wire wrapped round the transformer it will step the voltage up (step up transformer.) If the second side has less turns, the voltage will be stepped down (step down transformer.)


6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field and describe the factors which affect the size of the induced voltage

rotate a magnet in a coil of wire and there will be a current induced, the same is true for rotating a coil of wire in a magnetic field.

Factors that increase the electricity generated include: strength of magnetic field; number of coils in wire; speed of rotations.

6.15 understand that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it and describe the factors which affect the size of the induced voltage

If you move a wire back and forth across a magnetic field a voltage will be induced.

If you move a magnet back and forth through a coil of wire a voltage will be induced.

If you increase the magnetic field strength, quicken the movement or increase the coils of wire you can increase the voltage induced!

Friday, 3 May 2013

6.14 describe how the force on a current-carrying conductor in a magnetic field increases with the strength of the field and with the current.

If you have a wire in a magnetic field, if you increase the current there will be more force on the wire; if you increase the strength of the magnetic field there will be more force on the wire.

6.13 use the left hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field

The magnetic field finger is pointing south. The current finger is pointing negative.

6.12 understand that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers

If there is a wire- with a current running through- in a magnetic field it will experience a force ie it will be pushed up or down.

In a DC motor, there is a wire in a magnetic field. The force it experiences turns it around, this turns a 'split ring commutator' this basically is where charge goes from 'brushes' into the wires. The best way to understand them is with an animation or picture:

In a loud speaker, a coil is in a magnetic field. When a current is run through it the wire will experience a force that pushes it away from the field, this in turn pushes a cone which makes the sound. Whatever frequency the AC current is at, the coil will move at that frequency, making a note of a certain pitch.

6.11 understand that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field

if something with a charge is moving across a magnetic field, it will experience a force from the field. Unless of course it is parallel in which case it wont need to as it is already in a place the field would want to move it to.

6.10 sketch and recognise magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current

a field around a straight wire is simply a series of circles around the wire.

A field around a solanoid is similar to that of a bar magnet.

A field around a flat coil is basically like a single wire, but there are two.

6.9 describe the construction of electromagnets

A piece of wire is wrapped around a soft magnetic material. When there is a current in the wire, a magnetic field is induced in the metal.

Tuesday, 30 April 2013

6.8 understand that an electric current in a conductor produces a magnetic field round it

If you run an electric current through anything that conducts (e.g. a wire) a magnetic field will be produced around it!

6.7 describe how to use two permanent magnets to produce a uniform magnetic field pattern.

If you put two bar magnets together with their north and south touching, then they will form the same magnetic field as if there were one bar magnet.

'hold two opposite poles close to each other so that they attract as this makes a uniform magnetic field'

6.6 describe experiments to investigate the magnetic field pattern for a permanent bar magnet and that between two bar magnets

To track field lines you can use iron filings, which are magnetic materials, which will line up along the magnetic field. and you can use compasses which will show that the lines go from north to south. The following results will occur:

6.5 understand that magnetism is induced in some materials when they are placed in a magnetic field

Some materials that are not magnetic can become one when they are in a magnetic field. This is because the magnetic field encourages its electrons to align and form poles. This can happen in iron (and steel), cobalt and nickel.

6.4 understand the term ‘magnetic field line’

Magnetic field lines represent the shape and direction of a magnetic field.
Its important to realise that these lines only represent the field and that the spaces in-between the lines are not in fact spaces in the field, a field is also three dimensional, so the lines just give an idea.

6.3 describe the properties of magnetically hard and soft materials

A magnetically hard material retains its magnetic properties for a long period of time/ permanently  They are hard to demagnetise.

A magnetically soft material looses its magnetic properties almost as soon as it leaves a magnetic field.

6.2 understand that magnets repel and attract other magnets and attract magnetic substances

Opposite poles of magnets attract.
Like poles of magnets repel.
Magnetic substances can also be attracted by a magnet.

6.1 use the following units: ampere (A), volt (V), watt (W)

ampere (A)
volt (V)
watts (W)

Thursday, 25 April 2013

5.17 use the relationship between the pressure and volume of a fixed mass of gas at constant temperature

p1V1 = p2V2

5.16 use the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume

The higher the Kelvin the higher the pressure.

If volume and mass are kept the same, then increasing one will increase the other in direct proportion.


5.15 describe the qualitative relationship between pressure and Kelvin temperature for a gas in a sealed container

As Kelvin increase, energy increases. As the energy of something increases, its particles will move faster and with more force. This will mean more force is exerted over a fixed area- increasing pressure.

So if a gas has its kelvin increased, it will exert more force on the container its in, meaning the pressure will go up.

5.14 understand that the Kelvin temperature of the gas is proportional to the average kinetic energy of its molecules

The Kelvin temperature scale is in direct proportion to the energy of particles.

Because it puts 0 where particles have no energy, as the Kelvin go up so does the energy.

5.13 understand that an increase in temperature results in an increase in the average speed of gas molecules

If you increase the temperature of something, you increase the energy levels in it. The molecules of it will then have more kinetic energy- this means they will be travelling faster.

5.12 describe the Kelvin scale of temperature and be able to convert between the Kelvin and Celsius scales

The kelvin temperature scale uses absolute zero as a starting point.
Absolute zero is 0 Kelvin.

Absolute zero is -273°C

0 kelvin = -273°C

273 Kelvin = 0°C

1 Kelvin = -272°C

274 Kelvin = 1°C

Above are examples of how to convert between the two, as you can see I have just just a solving equations method to work out different values (eg what you do to one side you must add to the other.)

5.11 understand why there is an absolute zero of temperature which is –273°C

Heat is energy, the more energy the more heat. If something were to have no energy it would be 'absolute zero'.

Zero in Celsius is the freezing point of water, 'absolute zero' is -273°C

5.10 understand that molecules in a gas have a random motion and that they exert a force and hence a pressure on the walls of the container

Molecules of gas move randomly about space. When the collide with a surface, they exert pressure on it. For example air particles collide with the surface of a balloon, the pressure the exert keeps the balloon inflated.

5.9 understand the significance of Brownian motion, as supporting evidence for particle theory

Brownian motion is the principle that particles move randomly about a space.
Particle theory says that as particles move about (randomly) they collide, when they collide with a surface the exert a pressure on the surface (like air keeping a balloon inflated.)

5.8 describe the arrangement and motion of particles in solids, liquids and gases

Solid: low energy; little movement, vibrating on the spot

Liquid: some energy; some movement; particles collide, bouncing apart and creating space between particles

Gas: lots of energy; lots of movement; particles collide a lot, bouncing apart more creating lots of space between particles 

5.7 understand the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas

Particles in a solid don't move; but if they are heated they gain energy and move, if they move enough they will become a liquid because the particles will bounce off each other moving them further apart.
Similarly, a liquids particles have some energy, but if they gain more they will bounce off each other more frequently moving them further apart; eventually they are far enough apart that it is a gas.

5.6 know and use the relationship for pressure difference

pressure difference = height × density × g

p = h ×ρ × g

5.4 know and use the relationship between pressure, force and area

Pressure= force/ area

p = F/A

5.3 describe experiments to determine density using direct measurements of mass and volume

Using a set mass of one object (eg 100g of water) change the space its in (eg 200ml cylinder taking ten off the ml each time.) Use the formula mass/volume to find the density, it will go up as the volume decreases.

5.2 know and use the relationship between density, mass and volume

Density= mass/ volume

p= m/V

5.1 use the following units

degrees Celsius (oC)
kelvin (K)
joule (J)
kilogram (kg)
kilogram/metre3 (kg/m3)
metre (m)
metre2 (m2 )
metre3 (m3)
metre/second (m/s)
metre/second2 (m/s2 )
newton (N)
pascal (Pa)

3.25 describe how digital signals can carry more information

  • larger bandwidth

4.16 describe the energy transfers involved in generating electricity using several different methods

  • wind- the kinetic energy from the wind, turns a turbine which turns a generator which produces electrical energy
  • water- Kinetic energy from water, turns a turbine which turns a generator which produces electrical energy
  • geothermal resources- Thermal energy heats water, water turns into steam, the thermal energy of the steam turns a turbine which then has kinetic energy, the turbine turns a generator which produces electrical energy
  • solar heating systems- Light energy from the sun into thermal energy in water
  • solar cells-convert light energy from the sun into electrical energy
  • fossil fuels- Chemical energy is burnt to form heat energy, this turns into heat energy in water, this turns into kinetic energy in a turbine, this turns into electrical energy in a generator.
  • nuclear power- kinetic energy in uranium, heat energy in water, kinetic energy in turbine, electrical energy in generator.

Tuesday, 23 April 2013

4.15 use the relationship between power, work done (energy transferred) and time taken

Power= work/ time

4.14 describe power as the rate of transfer of energy or the rate of doing work

Power is the rate of work,
Power is also the rate of energy transfer.
So power is how quickly these processes are done.

4.13 understand how conservation of energy produces a link between gravitational potential energy, kinetic energy and work

The best way to explain this idea is with a swinging pendulum:
At the top of the swing, it will have its highest gravitational potential energy (as its further from the earth); but it will have its lowest kinetic energy (it slows to a stop at the top point).
At the bottom of the swing, it will have its lowest gravitational energy (as it is closer to the earth); but it will have its highest kinetic energy (it goes very quickly past the bottom point).

Between the points work (force x distance) is constantly being done: the pendulum is moving through space.
Remembering that work done is equal to energy transferred, we can see that as work is done that moves the pendulum upwards, kinetic energy is transferred in to gravitational potential energy. When work is done to bring the pendulum downwards, energy is transferred from GPE to KE.

The pendulum demonstrates that energy is conserved, as then energy is constantly changing between different forms. The only reason that energy is lost from the pendulum, and it slows down, is that some energy is transferred into heat or sound.

maximum kinteic energy at lowest point of swing - minimum gravitational potential energy. at the highest point of swing there is no kinetic energy, and maximum gravitational potential energy.

4.12 know and use the relationship between kinetic energy, mass and speed

Kinetic energy = 1/2 x mass x velocity²

KE= 1/2 × m × v²

4.11 know and use the relationship: gravitational potential energy = mass × g × height

gravitational potential energy = mass × g × height
GPE = m × g × h

It may be useful to think that mass, gravity and height are all things that increase GPE.

4.10 understand that work done is equal to energy transferred

Work done and energy transferred are always the same.

4.9 know and use the relationship between work, force and distance moved in the direction of the force

work done = force × distance moved
W = F × d

4.1 use the following units: kilogram (kg), joule (J), metre (m), metre/second (m/s), metre/second2 (m/s2), newton (N), second (s), watt (W).

kilogram (kg),
joule (J),
metre (m),
metre/second (m/s),
metre/second2 (m/s2),
newton (N),
second (s),
watt (W)

Tuesday, 16 April 2013

4.8 explain how insulation is used to reduce energy transfers from buildings and the human body.

An insulator is something that is bad at conducting. If something with heat energy is surrounded by an insulator, it wont lose heat by conduction. This is true in buildings where insulating materials are put in walls and on floors to stop heat being lost from inside. This is the same in humans where we wear clothes to stop heat being lost from conduction. Air is a poor conductor, so materials with many air gaps in are also poor conductors; air trapped between double glazing prevents heat loss through windows.

4.7 explain the role of convection in everyday phenomena

Convection is helpful as it distributes heat energy. This is useful in many situations, for example, a radiator in one place will be able to heat a whole room, as hot air will rise away from it creating a current of cool air to be heated.

4.6 describe how energy transfer may take place by conduction, convection and radiation

Conduction is when energy is passed from one particle to another via contact. For example heat is passed from your skin to a window when they touch.

Convection is when particles with energy rise, the space they leave is filled by other particles. If the source of energy continues these new particles will also gain energy, they will then rise and the process will be repeated.

Radiation is when heat is transferred as infra red waves. These waves can travel through space and be conducted or reflected.

These energy transfers are all for heat energy.

4.5 describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the above relationship, including their representation by Sankey diagrams

With all devices that aim to use energy for a reason, some of the energy put in to run it comes out as a non useful form of energy. The more energy that comes out as useful, the more efficient the object is. For instance, a light bulb wants to create light energy, but it creates heat at the same time. This is the same for many processes: a fire (for warmth) creates light; a pepper grinder creates sound (even though you just want it to move).
Sankey diagrams use an arrow to represent the energy going in and out of a process:
Here 100j of energy is going in. All 100j must come out. 90j come out as heat, 10j come out as light.

4.4 know and use the relationship between useful energy output, total energy input and efficiency

useful energy output / total energy input= efficiency

4.3 understand that energy is conserved

Energy can never be lost, only transferred. Energy will always carry on, just in a different form.
For example, when you switch on a light, you are not loosing energy from a battery (chemical), you are just converting it to light energy!

4.2 describe energy transfers involving the following forms of energy: thermal (heat), light, electrical, sound, kinetic, chemical, nuclear and potential (elastic and gravitational)

Energy can change from one form to another, and frequently does. Some examples include:
Chemical energy in food turns into kinetic energy for movement;
Electrical energy in a circuit turns into heat energy in a resistor;
Kinetic energy in your muscles turns into sound energy from you voice.
Elastic potential energy in a taught rubber band turns into kinetic energy when it sails through the air.

3.32 relate the loudness of a sound to the amplitude of vibration.

The bigger the vibration the higher the amplitude.
The higher the amplitude the louder the sound.

3.31 relate the pitch of a sound to the frequency of vibration of the source

The more something vibrates the higher frequency.
The higher frequency the higher pitch.
So the more vibrations the higher pitch.

This video demonstrates this concept well, but is really quite an odd clip:

3.30 describe an experiment using an oscilloscope to determine the frequency of a sound wave

Have an noise made into a microphone attached to an oscilloscope, for example have someone try to sing a note. See how many oscillations there are per second, this will be your frequency. Try changing the pitch of the note and see it the number of oscillations per second changes.

An oscillation is the completion of one wave i.e from one peak and the next.

3.29 understand how an oscilloscope and microphone can be used to display a sound wave

A microphone detects sound waves, it can feed this information into an oscilloscope which will display it as a wave (or straight line.) Here is an example of what an oscilloscope displays:

3.28 describe an experiment to measure the speed of sound in air

Measure the distance between two places, have a sound made in one place, as soon as you see the sound has been made start a stop watch, as soon as you hear the sound made stop the stopwatch.

distance/time= speed

3.27 understand that the frequency range for human hearing is 20 Hz – 20,000 Hz

The human ear can pick up a limited section of different frequencies of sound: that is between 20 and 20,000 Hertz.

2.25 explain some uses of electrostatic charges, eg in photocopiers and inkjet printers.

There are some events in which having two objects of opposite charge is very useful. An example of this is in photocopiers and inkjet printers where the ink is given a charge, and the parts of the paper where its wanted is given the opposite charge, so that the ink is automatically attracted to the right parts of the paper.

2.24 explain the potential dangers of electrostatic charges, eg when fuelling aircraft and tankers

When a large electrostatic charge builds up it can create a spark. When refuelling vehicles the fuel rubbing along the pipe can cause an electrostatic charge, if this sparks if could ignite the fuel causing a fire or explosion. (This can be avoided if the charge is brought to earth by a wire attached to the plain or tanker)

2.23 explain electrostatic phenomena in terms of the movement of electrons

Electrostatic phenomena is an event where static electricity has a specific effect: for example a static shock. Electrons move from one material to another, the material with a negative charge will then look for some way to earth its charge: like clouds through lightening or a car through your hand and body.

Tuesday, 9 April 2013

2.22 understand that there are forces of attraction between unlike charges and forces of repulsion between like charges

Opposite forces attract.
Similar forces repel.

2.21 explain that positive and negative electrostatic charges are produced on materials by the loss and gain of electrons

If two materials are rubbed along each other one will gain electrons from the other.
The one that has gained electrons has a negative charge. The one that has lost electrons will have a positive charge. The charges are electrostatic because they are not flowing.

2.20 describe experiments to investigate how insulating materials can be charged by friction

Get a polyethene rod and rip up some small pieces of paper; the rod will have no effect on the paper.
Rub the polyethene rod with a cloth, now the rod will attract the pieces of paper, this is because it now has a charge they are attracted to.

2.19 identify common materials which are electrical conductors or insulators, including metals and plastics

Electrical conductors are materials that allow a current to pass through them. To do this they need to have 'free' electrons, because current is a flow of electrons. Metals have free electrons because of the way they are bonded (atoms and electrons within a lattice) this means they are good electrical conductors.
Plastics are polymers which are bonded in a way that means electrons aren't free and so can't move. No flow of electrons means no electric current so they are insulators.

2.18 understand that:  voltage is the energy transferred per unit charge passed  the volt is a joule per coulomb.

Often people think of voltage as if it were something pushing current through a circuit, which is helpful, but more accurately its the energy transferred per unit of charge passed.
The unit volt is a joule per coulomb. These are things that simply need to be learnt.

2.17 know that electric current in solid metallic conductors is a flow of negatively charged electrons

Electric current is a flow of electrons, so when there is an electric current in a metal, the electrons in the metal are flowing.

2.16 know and use the relationship between charge, current and time

charge = current × time
Q = I × t

2.15 understand that current is the rate of flow of charge

Current is the rate at which charge is flowing through a circuit.
'It is like the flow of water through a set of pipes'

2.14 know and use the relationship between voltage, current and resistance

voltage = current × resistance
V = I × R

2.13 know that lamps and LEDs can be used to indicate the presence of a current in a circuit

For an LED to light up there must be a current in a circuit. If a LED is in a circuit but not emitting light then there must be no current. If an LED is illuminated then it will have a current flowing through it. By this we know that if the LED in our circuit is shining then there is a current, if it isn't then we don't.

2.12 describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature

An LDR is a light dependent resistor. Its resistance changes with the intensity of light: the brighter it is the less resistance; the less light the more resistance.

Thermistors are temperature dependent resistors. In hot conditions there will be less resistance where as in the cold the resistance is high.

2.11 describe the qualitative effect of changing resistance on the current in a circuit

Increasing the resistance will decrease the current. This can be achieved by adding more components or ones with higher resistance.
Decreasing the resistance will increase the current. This can happen if components are removed or replaced by those with lower resistance.

2.10 describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how this can be investigated experimentally

If you increase the resistance the current will decrease. resistors, metal filament lamps and diodes all create resistance in a circuit and so will decrease the current.
This can be investigated using an ammeter and measuring the current with and without these components, or with different voltage levels (measured by voltmeter.)

Saturday, 30 March 2013

2.9 understand that the current in a series circuit depends on the applied voltage and the number and nature of other components

The current in a series circuit is the same through out all parts of the circuit. It is worked out using the equation I= V/R. So its the total of the voltages received by the components divided by the total of all the components resistances.

2.8 explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting

In a series circuit everything is connected on one line. This means that the voltage is shared out between every component: this makes it useful for supplying low power things like fairy lights.

In a parallel circuit different components are connected separately to the supply. This means that of one component breaks the others can continue being powered as the whole circuit is still functioning, this makes it practical to use. It is also good for charging higher power things as the potential difference is equal all over a parallel circuit so each component receives the full voltage.

2.7 understand the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery

Direct current flows in one direction only. It is supplied by cells and batteries. It comes out as a straight line on an oscilloscope.

Alternating current changes from one direction to another rapidly. Mains electricity is alternating (interestingly this is because the electricity has to go through transformers on the national grid which only work on ac current, although that's not relevant here!)

2.6 use the relationship between energy transferred, current, voltage and time

energy transferred = current × voltage × time
E = I × V × t

n.b this is the same thing as saying power x time

2.5 know and use the relationship: power = current × voltage

power = current × voltage
P = I × V

2.4 understand that a current in a resistor results in the electrical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts

As a resistor slows down the movement of electrons, the kinetic energy that was moving them is converted into heat energy. This can be used, for example, in hair dryers or heaters.

2.3 understand the uses of insulation, double insulation, earthing, fuses and circuit breakers in a range of domestic appliances

Insulation is covering a live wire with a material that won't conduct the electricity.
Double insulation is a precaution that makes sure the live wire cannot touch the casing (so no shock can be conducted) usually by putting extra insulation round that wire. Double insulation can also mean that the casing of an object is plastic so even if the wire touches it, it wont conduct.
An earth wire is touching the case so that if a current is in the case, it will be directed through the earth wire, this will then take the current to the earth. Additionally the surge of electricity in the wire may break the fuse.
Fuses are sections of wire in the circuit that melt if too high a current goes through them. They come with different maximum currents.
Circuit breakers have an electromagnet that is activated if the current goes above a certain limit. the electromagnet pulls an iron switch towards it, this opens the switch and breaks the circuit.

3.26 understand that sound waves are longitudinal waves and how they can be reflected, refracted and diffracted

Sound waves are longitudinal waves (the one that looks like a bar code.) They can be reflected, refracted and diffracted much like light can. For example an echo is a reflection of sound.

2.2 understand and identify the hazards of electricity including frayed cables, long cables, damaged plugs, water around sockets, and pushing metal objects into sockets

In frayed cabling the insulation has worn down exposing live wires, electricity can be conducted from these.
Longer cables are at a higher risk of being damaged and there is more resistance with longer wires making them more at risk of over heating.
Damaged plugs create a risk that some of the safety features may be broken.
Water conducts electricity and can cause energy from the circuit to flow trough it creating a fire and electrocution risk. Metal objects in sockets have the same dangers.

Sunday, 3 March 2013

3.24 describe the advantages of using digital signals rather than analogue signals

The term noise means the random signals picked up by waves. Radios may crackle or internet may looses connection. This effects analogue signals badly as each time it is amplified the noise also gets amplified, this alters the signal making it hard or impossible to identify as the original signal.

In digital signals any noise picked up is likely to be of a smaller amplitude than that if the on state, this means something receiving it will ignore the noise as it is neither on nor off, this makes them less likely to be distorted.

3.23 understand the difference between analogue and digital signals

The amplitude and/or frequency constantly vary.

the signal is a wavy line that goes up and down in an uneven pattern

Consists of pulses with two states: on; off
the signal is a continuous line that goes up, down and across in straight lines with no curves

3.22 know and use the relationship between critical angle and refractive index

sin(critical angle)= 1/ refractive index

sin(c)= 1/n

3.21 explain the meaning of critical angle c

When light travels from one medium to another it is refracted; it changes angle due to change in density.
Past a certain angle the light will simply be refracted back into the medium it is in, this angle is the critical angle.

3.20 describe the role of total internal reflection in transmitting information along optical fibres and in prisms

Beyond the critical angle, light will be reflected back into the medium they came from at the same angle. In this way they are trapped in the medium.
By reflecting light past its critical angle you can make it travel through a medium to send information: this is done in optical fibres.
Diagram showing how light reflects inside a glass fibre - the light "zig-zags" from one side of the fibre to the other

3.19 describe an experiment to determine the refractive index of glass, using a glass block

Shine a ray of light through a glass block, measure the angle of incidence and the angle of refraction.
Do sin(i) divided by sin(r) and you will have the refractive index of glass.

3.18 know and use the relationship between refractive index, angle of incidence and angle of refraction:

Refractive index= sin (angle of incidence)/ sin (angle of refraction)

n= sin(i)/ sin(r)

3.17 describe experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms

Place a block of glass on a piece of paper, drawing an outline.
At one point, draw the normal line.
Draw a line at 30 degrees to the normal line, shine a ray of light down this line.
Draw a line where the light comes out the other side. Connect the two lines, drawing the refracted ray.
Measure the angle of the emergent ray.
Repeat for different shaped glass.

3.16 construct ray diagrams to illustrate the formation of a virtual image in a plane mirror

The mirror- a straight line with hatchings to show the side with the reflective coating on it.
Incident ray- line with arrows pointing towards the mirror.
Reflection ray- line with arrows pointing away from the mirror.
The image- (where the reflection appears to be behind the mirror) dashed line.

The angle of incidence should equal the angle of reflection.
A perpendicular line from the object to the mirror, if repeated the other side of the mirror, shows where the image appears to be in the mirror. Draw a line from the image to the eye, where this passes the mirror is where the angle of incidence should also meet the mirror.


3.15 use the law of reflection (the angle of incidence equals the angle of reflection)

The angle of incidence is the angle that light hits a mirror; it is taken between 90 degrees from the mirror and the incidence wave (the wave that hits the mirror.)

The angle of reflection is the angle that light leaves the mirror; it is taken between 90 degrees from the mirror and the angle of reflection.

The angle of incidence is always the same as the angle of reflection.

3.14 understand that light waves are transverse waves which can be reflected, refracted and diffracted

Light hitting a reflective surface will 'bounce' back from the surface (at the same angle they hit the surface.)

Light waves change speed when they pass through objects of different densities, this causes them to change direction. When they return to the original density they will continue in the original direction.

When light meats a barrier, it will carry on through the gap and spread out in the area beyond.

3.13 understand the detrimental effects of excessive exposure of the human body to electromagnetic waves and describe simple protective measures against the risks.

  • microwaves: internal heating of body tissue
    • this can damage cells if they overheat
  • infra-red: skin burns
    • skin cells are damaged by overexposiure
  • ultraviolet: damage to surface cells and blindness
    • can damage receptor cells in the retna
  • gamma rays: cancer, mutation
    • can cause cells to change their arrangement causing cancer

People tend to avoid long term low level exposure or short term high level exposure. Sun creames can protect against UV as can sun glasses.

3.12 explain some of the uses of electromagnetic radiations

  • radio waves: broadcasting and communications
    • Vibrations carry sound
  • microwaves: cooking and satellite transmissions
    • Vibrations create heat.
  • infra-red: heaters and night vision equipment
    • Vibrations create heat, cameras can detect where it is high and low to see by heat.
  • visible light: optical fibres and photography
    • Light reflected down tube to send signals, or onto film to take photos.
  • ultraviolet: fluorescent lamps
    • A coating inside the bulb will absorb UV light and re-emit it as visable light.
  • x-rays: observing the internal structure of objects and materials and medical applications
    • They pass through skin and soft tissue but reflect hard structures like bone.
  • gamma rays: sterilising food and medical equipment

3.11 identify the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colours of the visible spectrum

As you go up the electromagnetic spectrum wavelength decreases and frequency increases.
The same is true for visible light; with red being the longest wavelength and lowest frequency and violet being the shortest wavelength and highest frequency of all visible light.

3.10 understand that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space

The electromagnetic spectrum is a range of different frequency waves, one section of the spectrum is visible light (light we can see.) All of the waves in the electromagnetic spectrum travel at the same speed when they are in a vacuum.

3.9 understand that waves can be diffracted through gaps, and that the extent of diffraction depends on the wavelength and the physical dimension of the gap.

Diffraction can happen through a gap, when waves go through a narrow space, on continuing they spread out again. The smaller the gap, in comparison to the wave length, the larger the diffraction.

3.8 understand that waves can be diffracted when they pass an edge

As this diagram shows, when a wave hits an edge, as it carries on it spreads out into the space beyond the edge. This happens with radio waves and hills, and water and islands.

3.7 use the above relationships in different contexts including sound waves and electromagnetic waves
Wave speed= frequency x wave length
Frequency= 1/time period

You should be able to manipulate these equations to answer questions that may ask in a different order; use the triangle method.

3.6 use the relationship between frequency and time period

Frequency= 1/ time period

3.5 know and use the relationship between the speed, frequency and wavelength of a wave

wave speed = frequency × wavelength
v = f × λ

3.4 understand that waves transfer energy and information without transferring matter

A wave is a transfers energy through a space or object, but it does not move the particles in it.
If you stand on one side of a door and say 'Hi' a person on the other side will be able to hear you saying 'Hi'. This is because the vibrations that you made have travelled through the door to the other side, the energy moving from one particle of the door to another: but the door its self has not move, none of its particles have changed position.

3.3 define amplitude, frequency, wavelength and period of a wave

Period of a wave
Time taken for the source to produce one complete wave.

As a wave vibrates to either side of the direction of travel, the amplitude is the distance between the line of the direction of travel and the furthest point the it vibrates away from the line:
The number of waves per second, it is measured in Hertz (Hz). You can think of it as how quickly the waves are travelling.

The distance between one point on a wave and the same point on the next wave; usually the point from the top/bottom of one wave (peak/trough) to the top/bottom of the next.

3.2 understand the difference between longitudinal and transverse waves and describe experiments to show longitudinal and transverse waves in, for example, ropes, springs and water

Vibrations (osculations) go up and down along the line of travel,
Light and electromagnetic waves travel in this way,
If you drop something in water the waves move up and down as they travel outwards,
If you lie a piece of string on a table and move one end up and down, the movement will pass through the object to the other end.

The vibrations are in the same direction as the line of travel,
Sound waves travel in this way,
Compressions are where vibrations are close together, rarefactions are where they are more spread out,
If you push one end of a stretched spring the compression will move down the spring.

Watch these animations to see how the examples work:

3.1 use the following units: degree (°), hertz (Hz), metre (m), metre/second (m/s), second (s)

degree (°)- distance
hertz (Hz)- cycles per second
metre (m)- distance
metre/second (m/s)- speed
second (s)- time