OCR Physics P4 Revision

Dan Allibone
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OCR Physics P4 Revision cards

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Dan Allibone
Created by Dan Allibone almost 4 years ago
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Question Answer
Which radioactive materials are commonly used in smoke alarms and what do they emit? Uranium 241, americium and others and they emit alpha
What does static mean? Stationary
Name the charges of each : Proton, Electron and Neutron Positive protons Negative electrons Neutral neutrons
Electricity take the path of the least... Resistance
How does static electricity work? Use the terms; electrons, positive charge, negative charge and attraction One substance gains an electron from another and the previously neutrally charged substances become oppositely charged and hence attract.
Where are the following placed in a circuit and why : Ammeter, voltmeter Ammeter in the series as it always measures the current Voltmeter in parallel to the component being measured as it measures potential difference
What colour are the earth, live and neutral wires in a plug 138e101e-31f3-49e6-ae26-7574e95405d2.gif (image/gif)
what is the formula for calculating resistance? Resistance = voltage/current
Does a fuse actually blow? If not what does it actually do and why? It melts if the current in the circuit is above the capacity of the fuse.
Define ultrasound Sounds with a higher frequency than 20 000 Hz
What is the name of the other type of sound outside our hearing range and what frequency does it have? Infrasound and it has a frequency of 20 Hz and below
Name 3 uses of ultrasound Foetus imaging Breakdown of kidney stones Sonar Bone scans
What is alpha and what is its charge? A helium nuclei and a +2 charge
What is beta and what is its charge? A high speed electron with a -1 charge
What is gamma radiation and what is its charge? EM radiation and has a charge of 0 (neutral)
Define half life The time required for half the nuclei in a isotope to undergo radioactive decay
What type of curve is seen on radioactive decay graphs and why? Exponential curves because radioactive decay is a spontaneous process so it can go on indefinetly
What is ionisation? The process in which an atom gains or loses electrons to form an ion.
What is the charge of an ion? positive or negative
What type of reaction is nuclear fission? A chain reaction
How do CT scanners work? A series of x-rays are fired and then received on the other side of a tube which moves along the body and from this you can image what the x-rays passed through like the thickness of the tissue.
Why are high doses of radiation often safer than lower ones? Because they mutate and kill the mutated cells whereas lower doses will mutate the cells and leave them alive in the body which can cause cancer.
How do radioactive tracers work? They detect abnormalities in the body and are attracted and absorbed by the damaged areas. They emit gamma which means that it can leave the body and be detected by machines. They need a short half life so that they don't stay in the body too long.
Where does nuclear fusion occur naturally? In a stars core
Why is fusion good? It releases a lot of energy and the products are not radioactive.
Why don't we use nuclear fusion? Because it is currently infeasible on earth as it requires a very high temperature. Cold fusion has allegedly been performed once on earth and is currently being studied.