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Phy Paper 1 - Final Exams - Coggle Diagram
Phy Paper 1 - Final Exams
P1
L1 - Energy Transfers
Energy stores: Kinetic, electrical, chemical, GP, EP, nuclear, sound, heat, magnetic, electrostatic.
Energy can be transferred through: mechanical transfer, work done when current flows, thermally and through radiation.
L2 - Efficiency
Efficiency = Useful Energy Out / Total Energy In
L3 - Reducing Heat Loss
Conduction is exclusive to solids while convection can occur in fluids. Radiation can take place in vacuums.
In convection, hot air rises as it is less dense than cool air. As it rises, it begins to cool and a convection current is established.
Method:
Place a small beaker inside of a larger beaker.
Use a kettle to boil water, transfer a known volume of this into the small beaker.
Place a lid on the large beaker and place a thermometer through the whole in the lid (reduces heat lost to convection).
Record the starting temp of the water and begin a stopwatch. Record at regular time intervals.
Repeat with the same volume of hot water, using an insulator (same mass/thickness of insulator used each time).
Burning gas generates less carbon dioxide than burning coal and gas-fired power stations can be turned on quickly in periods of high demand while coal-fired plants have a long start-up time.
P2
L1 - Series and Parallel
From positive terminal to negative terminal (conventional current).
Ammeter = Series
Voltmeter = Parallel
In a parallel circuit, adding more resistors will decrease the total resistance as there are more branches through which current can flow.
L2 - Mains Electricity
In the UK, mains electricity is a 230V AC with a frequency of 50Hz.
Earth wire: Yellow and green wire, offers a low resistance 'pathway' to the ground, grounding the current if there are any faults in the device.
Neutral wire: Blue wire, simply completes the circuit and allows current to flow within.
Live wire: Brown wire, has 230V applied over it and is incredibly dangerous if touched.
L3 - National Grid
The national grid consists of a series of cables and transformers. Electricity is outputted by a power station, the potential difference is increased by step-up transformers; this is done to minimise the current to avoid energy being lost as heat.
L4 - Static Electricity
Electric field lines depict the direction that a positive charge would travel.
When electrons are added or removed from an insulator, it becomes charged. This will create a potential difference between the object and a grounded object. (Static electricity will only be generated with two insulators as electrons cannot flow through these).
P3
L1 - Density
To calculate the density of an irregular object, first find the mass of the object using an electronic balance. Then carefully place the object in a Eureka can filled with water. Collect the volume of water that the object displaces using a measuring cylinder.
L2 - Changing State
Internal energy is the sum of the kinetic energy (due to the motion of particles) and the potential energy (due to the position / arrangement of particles).
When a substance changes state, its temperature does not increase as all the energy that is being provided to the system contributes to its potential energy (arrangement of particles). This means that internal energy increases.
L3 - Specific Heat Capacity and Latent Heat
The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1kg of the substance by 1 degree celcius.
Specific latent heat is the amount of energy needed to change the state of 1kg of a substance with no change in temperature.
Latent heat of fusion = Solid to liquid
Latent heat of vaporisation = Liquid to vapour
L4 - Motion in Gasses
Particles in a gas are constantly moving in random directions at random speeds.
The pressure of a gas can be increased by increasing the temperature, decreasing the container volume or increase the volume of gas.
The pressure of a gas is inversely proportional to the volume: Pressure = Constant / Volume
When work is done on a gas, its internal energy increases (increase in temp).
P4
L1 - History of the Atom
Democritus and Dalton proposed that everything was made up of atoms and that atoms were indivisible.
JJ Thompson first proposed the plum pudding model: this depicted atoms as 'balls of positive charge' with small negative charges dotted throughout.
Rutherford's alpha scattering involved alpha particles being fired at a thin gold sheet (one atom thick). A florescent film would show when these particles made contact.
The Rutherford scattering showed that atoms were mostly empty space, contained a positively charged nucleus in which all its mass was concentrated.
L2 - Types of Radiation
Alpha - Same atomic structure as a helium nucleus (2 protons, 2 neutrons). Low penetrative properties, high ionisation properties, stopped with a sheet of paper.
Beta - High energy electron, released when a neutron decays into a proton and an electron. Medium ionisation and penetration, stopped with a few mm of aluminium.
Gamma - High energy EM wave, low ionising properties but high penetrative properties. A few cm of lead will stop most gamma radiation but not all.
L3 - Half-Life
Half-life is the average time it takes for the activity of an isotopic sample to half / the average time taken for the number of unstable nuclei in an isotopic sample to half.
Radioactive decay is a random process but half-life can be predicted is a large enough sample is used.
L4 - Background Radiation
Radioactive contamination is the state of possessing unwanted nuclear material within a system. This can occur due to ingestion. The object becomes radioactive.
Irradiation is the state of being exposed to radioactive source externally, this does not make the object radioactive.
Direct damage is caused by radiation colliding directly with the body's cells whilst indirect damage is caused by ionisation (causing random mutations) to the body's cells.
Some natural sources of radiation include cosmic rays, trace amounts of radon gas from the ground and medical appliances.
L5 - Uses of Radiation
In radiotherapy, a concentrated gamma ray will be fired, targeting a specific tissue. Because gamma has some ionising properties, it will damage and destroy the DNA of the tissue.
Radioactive sources can be used as tracers, a source emitting gamma may be ingested, it will collected in certain areas that are more dense (such as a tumour).