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.