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Physics - Coggle Diagram
Physics
Electricity
AC - alternating current, flow of electric charge that periodically reverses direction
DC - direct current, flow of electric charge in only one direction
Current - the flow of electrons, or charge around a circuit
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Current stays the same in a series circuit and splits between the different branches in a parallel circuit
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Potential difference is shared between components in a series circuit and stays the same in branches of a parallel circuit
As resistance in a circuit increases the current decreases as it is harder for the electrons to flow
Plug
a device for making an electrical connection between an appliance and the mains, consisting of an insulated casing with metal pins that fit into holes in a socket.
Brown - live wire and is held at a voltage of 230 V and provides the current, is on the right
Blue - neutral wire and completes the circuit, is on the left
Green and yellow stripes - earth wire and is a safety wire to stop the appliance becoming live, is at the top
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The National Grid
The National Grid distributes electricity across the country. The National Grid connects power stations to homes, workplaces and public buildings all around the country. The electricity may be produced by a conventional power station turning a generator or by another method.
An iron core transformer, with the primary coil on the left hand side and secondary coil on the right hand side.
Transformers are used to change voltages and currents in transmission lines. A transformer is formed from two coils of wire around a magnetic core. The number of coils determines whether the transformers will step-up or step-down the voltage.
As the power transferred must stay the same: increasing voltage decreases current, decreasing voltage increases current
In the National Grid, a step-up transformer is used to increase the voltage and reduce the current. The voltage is increased from about 25,000 Volts (V) to 400,000 V causing the current to decrease. Less current means less energy is lost through heating the wire.
To keep people safe from these high voltage wires, pylons are used to support transmission lines above the ground.
Before reaching the end user, a step-down transformer, reduces the voltage from the transmission voltage to the safer voltage of 230 V for home use.
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An IV graphs for a linear circuit element - potential difference vs current
An IV graph for a filament bulb - current vs potential difference
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In an electric field a charged particle, or charged object, experiences a force. If the forces acting on any object are unbalanced, it will cause the object to accelerate.
If two objects with the same charge are brought towards each other the force produced will be repulsive, it will push them apart.
If two objects with opposite charges are brought towards each other the force will be attractive, it will pull them towards each other.
When insulating materials rub against each other, they may become electrically charged . Electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. The material that gains electrons becomes negatively charged. The material that loses electrons is left with a positive charge.
Energy
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A system is a group of objects that can transfer energy between them e.g. a bouncy ball hitting a table
Energy moves from one part of a system to another e.g. electrical energy in iron is transferred to thermal energy
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Specific heat capacity is the amount of energy needed to increase the temperature of 1kg of a substance by 1'C
To reduce energy loss in abuilding you can have thick walls which are made of a low thermal conductor, thermal insulation, cavity walls, lot insulation, double/ triple glazed glass and draught excluders
If something transfers the same amount of energy in a longer time, it is less powerful
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The hotter an object is, the more infrared radiation will be emitted. If an object is hotter than its surroundings it will emit more infrared radiation than it is absorbing, thus meaning that the object will cool down.
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If an object is cooler than its surroundings, it will emit less radiation than it is receiving and will therefore heat up. The greater the temperature difference between an object and its surroundings, the faster energy is transferred.
Dark and matte surfaces absorb infrared radiation better than light shiny surfaces. Dark and matted surfaces also emit more radiation than light and shiny surfaces. Light and shiny surfaces tend to reflect a lot of infrared radiation that falls on them.
Matter
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As you increase the temperature of a gas, the pressure increases
Solid - low energy, vibrate around a fixed position, regular pattern and very close together
Liquid - greater energy, move around each other, randomly arranged and close together
Gas - highest energy, move quickly in all directions, randomly arranged and far apart
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particles gain energy and break some of the bonds between particles during melting and overcome the remaining forces of attraction between particles during evaporating or boiling
The amount of energy needed to change state from solid to liquid, and from liquid to gas, depends on the strength of the forces between the particles of a substance. The stronger the forces of attraction, the more energy is required.
Energy is transferred from a substance to the surroundings when a substance condenses or freezes. This is because the forces of attraction between the particles get stronger.
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A latent heat graph During a change of state a substance does not change temperature
Pressure
The pressure of a gas causes a net outwards force at right angles to the container. There is also a force on the outside of the container due to the pressure of the gas around it. If a container can easily change its size then any change in these pressures will cause the container to compress or expand due to the overall force
Boyle’s law - decreasing the volume of a gas increases the pressure of the gas. An example of this is when a gas is trapped in a cylinder by a piston. If the piston is pushed in, the gas particles will have less room to move as the volume the gas occupies has been decreased.
A piston closes the end of a cylinder with some gas molecules inside. The pressure applied to the piston is doubled and the volume inside the cylinder halfs.
As the pressure applied to a piston is doubled, the volume inside a cylinder is halved
Because the volume has decreased, the particles will collide more frequently with the walls of the container. Each time they collide with the walls they exert a force on them. More collisions mean more force, so the pressure will increase.
When the volume decreases, the pressure increases. This shows that the pressure of a gas is inversely proportional to its volume.
Radiation
Atoms
Atoms are made of neutrons and protons in a nucleus, and electrons in shells around it
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Electron - a stable subatomic particle with a charge of negative electricity, found in all atoms and acting as the primary carrier of electricity in solids
Proton - a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron
Isotope - each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei
Ion - an atom or molecule with a net electric charge due to the loss or gain of one or more electrons
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Decay
Radioactive atoms decay, this process is random and spontaneous
The rate of which this decay happens is called activity, and is measured in Becquerel (Bq)
Alpha
If the nucleus has too few neutrons, it will emit a ‘package’ of two protons and two neutrons called an alpha particle.
An alpha particle is also a Helium-4 nucleus, Helium ion, two neutrons, two protons and no electrons.
Alpha decay causes the mass number of the nucleus to decrease by four and the atomic number of the nucleus to decrease by two.
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Alpha (α) - penetrating power can't get through skin/paper, it has high ionising power and its range in air is < 5cm
Smoke alarms - alpha radiation ionises the air, allowing a small current to flow between two electrodes. Alpha is weakly penetrating so smoke stops it, the current drops and the alarm goes off.
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Beta
If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron. This electron is called a beta (β) particle - this process is known as beta radiation.
A beta particle has a relative mass of zero, so its mass number is zero, beta decay causes the atomic number of the nucleus to increase by one and the mass number remains the same.
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Beta (β) - penetrating power can't get through 3 mm of aluminium foil, it has low ionising power and its range in air is ≈ 1m
Controlling the thickness - the thickness of paper or metal is monitored by how much beta radiation is received at the detector. Alpha wouldn’t penetrate the paper. Gamma is so penetrating that there would be little difference in the reading detected if the paper became thick.
Radiation detectors - doctors may use radioactive chemicals called tracers for medical imaging. Certain chemicals concentrate in different damaged or diseased parts of the body, and the radiation concentrates with it. Radiation detectors placed outside the body detect the radiation emitted and build up an image of the inside of the body
Gamma
High energy particles will emit energy as they drop to lower energy levels. Since energy levels in the nucleus are much higher than those in the gas, the nucleus will cool down by emitting a more energetic electromagnetic wave called a gamma ray.
Gamma ray emission causes no change in the number of particles in the nucleus meaning both the atomic number and mass number remain the same.
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Gamma (γ) - penetrating power can't get through lead/concrete, it has very low ionising power and its range in air is > 1km
Leaks in pipes - water supplies can be contaminated with a gamma-emitting radioactive isotope to find leaks in pipes. Where there is a leak, contaminated water seeps into the ground, causing a build-up of gamma emissions in that area.
Sterilisation - sterilises surgical equipment to get rid of any bacteria and can be done without high temperature's
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Nuclear Fission
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Nuclear fission is the splitting of a large atomic nucleus into smaller nuclei. The substance id struck by a neutron and splits and a new neutron is released causing a chain reaction
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Components of the System
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Coolant - this is heated up by the energy released from the fission reactions and is used to boil water to drive turbines in the power station
Control rods - these are raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction
Graphite core - graphite slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod
Nuclear fuel - the fuel is held in rods so that the neutrons released will fly out and cause nuclear fission in other rods
Nuclear Fusion
Nuclear fusion is when two small, join together to make one nucleus. They happen under high temperatures and pressure to form a nucleus
A way for particles to travel quickly is by being in a hot gas or in plasma.which is needs a high temperature and pressure
During the fusion they release energy which is because some of the mass of the nuclei is converted to energy and it only happens in atoms that have an atomic mass of less than 55
Background Radiation
Background radiation is all around us. Some of it comes from natural sources and some come from artificial sources. Some natural sources are cosmic rays, rocks and soil and living things. Some artificial sources include medical X-rays, radioactive fallout from nuclear weapons testing and radioactive waste from nuclear power stations
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