459117
Descripción
Fichas por Anna Hollywood, actualizado hace más de 1 año
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Creado por Anna Hollywood
hace casi 11 años
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| Pregunta | Respuesta |
| What does the law of electric charge state? | That like charges repel and unlike charges attract |
| What happens when a polythene rod is rubbed with a duster? | Electrons are transferred from the duster to the polythene, making the rod negatively charged |
| What happens when an acetate rod is rubbed with a duster? | Electrons are transferred from the acetate to the duster, leaving the rod positively charged |
| What will happen if someone touches something at a high voltage? | Large amounts of electric charge may flow through their body to the earth |
| Name 2 instances where static electricity can be annoying | -Dust attracted to the TV (an insulator) -Clothes made from synthetic material clinging to each other and body |
| Name 4 ways that people can avoid electric shocks | -Using an earth wire to take away build up of charge -Insulating rubber mats to stand on -Shoes with insulating soles -Fuel tankers connected by conducting cable to aircraft when refuelling |
| What products can carry away electric charge? | Anti-static sprays, liquids and cloths |
| How do dust precipitators work? | Putting highly charged wires in a chimney and plates (that are earthed to have opp charge). As dust passes wires become charged with same charged, then repelled. Attracted to plates, plates vibrated, dust falls. |
| Why are dust precipitators used? | It removes harmful particles from chimneys in factories that pollute the atmosphere. |
| How is static electricity used in paint spraying? | Spray gun is charged..paint particles have same charge..repel each other..fine spray..object has opp charge..attracts paint..little wasted |
| What happens if the object being painted has no charge? | It gains same charge as paint and repels further paint particles |
| How do defibrillators work? | Two paddles charged from high voltage supply..placed on chest firmly so good electrical contact..electric charge passed through..heart contracts |
| What does a variable resistor/rheostat do? | Changes the resistance |
| What qualities of wire makes a wire more resistant? | If they are longer and if they are thinner |
| For a fixed resistor, what happens when it is connected to a voltmeter? | The current increases |
| For a fixed power supply, what happens when the resistance increases? | The current decreases |
| What is resistance measured in? | Ohms |
| What does the live wire do in your house? | Carries a high voltage |
| What does the neutral wire do in your house? | It completes the circuit, allowing a return path for the current |
| What does the earth wire do in your house? | It is connected to the case of an appliance to prevent it from becoming live |
| What does a fuse do? | It contains a wire which melts, breaking the circuit, if the current becomes too large |
| What two things stop a person from receiving an electric shock and how? | The earth wire and the fuse because as soon as the case is 'live' a large current flows down the earth wire and the fuse 'blows' |
| What can you buy to save yourself buying a new fuse every time it blows? | A re-settable fuse (circuit breaker) |
| What is ultrasound? | A wave with a frequency higher than 20,000 Hz |
| What kind of wave does ultrasound travel as? | A pressure wave |
| What are the features of a longitudal sound wave? | -Can't travel through a vacuum...the denser the medium, the faster the wave -The higher the freq, the smaller the wavelength -The louder the sound...more energy carried..larger amplitude |
| What is the main difference between longitudal and transverse waves? | In a longitudal wave the vibrations of the particles are parallel to the direction of the wave. But in a transverse wave, the vibrations are at right angles to the direction of the wave. |
| How is ultrasound used to break down kidney stones? | High-powered US beam aimed at stones..breaks it into smaller pieces..pieces excreted from body |
| How is ultrasound used in a body scan? | At each boundary between the tissues some ultrasound is reflected, rest is transmitted...returning echoes are recorded and used to build image of internal structure |
| How can the internal structure be known? | Know speed of ultrasound and time echo takes to return. Multiply together to get distance. |
| What does the proportion of ultrasound returned tell us? | The densities of each of the adjoining tissues |
| What happens if the tissues are very different (e.g. blood and bone)? | Most US is reflected and very little is left to penetrate further into the body |
| What are the two advantages the US has over x-rays? | Able to produce images of soft tissue and doesn't damage living cells |
| What does nuclear radiation cause? | Ionisation which removes/gives an atom electrons |
| Is radioactive decay a random or a programmed process? | Random |
| Why will the count rate always be pretty much the same for a radioisotope? | Because there are so many atoms |
| What kind of nuclei does a radioisotope have and what does this mean? | An unstable nuclei and this means that their nuclear particles aren't held together strongly enough |
| What does it mean by 'the half-life' of a radioisotope? | The average time for half the nuclei present to decay. This cannot be changed |
| What are both protons and neutrons? | Nucleons (both found in nucleus) |
| What does a mean? z X | a=atomic mass z=atomic number X=chemical symbol for element |
| What are the 5 properties of an alpha particle? | Positively charged...large mass...helium nucleus...helium gas around it...2 protons and 2 neutrons |
| What happens to an element once it has been ionised by an alpha particle? | It mass number decreases by 4 and its atomic number decreases by 2 |
| What is the nuclear for alpha decay of uranium? | |
| What are the 4 main properties of a beta particle? | Negatively charged...very small mass...very fast...an electron |
| What happens to an element during beta decay? | The mass number is unchanged and the atomic number increases by one |
| What is the nuclear equation for beta decay of carbon? | |
| When is gamma radiation given off? | After alpha and/or beta particles are given off by an element, the nucleus may have surplus energy. This energy is given off in the form of gamma rays |
| What are the 3 things that background radiation is due to? | Radioactive substances in rocks and soil...cosmic rays from space...man-made sources (radioactive waste) from hospitals and industry |
| Name 3 types of background radiation | Food...rocks...medical...nuclear power...radioactivity in air...cosmic rays |
| How is a tracer used to locate a leak in an underground pipe? | Small amount of gamma emitter put in pipe...detector passed along ground above pipe...activity detected in leak region, none after this point |
| Why is gamma radiation used as a tracer? | Because the radiation is able to penetrate to the surface |
| How does a smoke detector work? | Alpha particles ionise air...creates current...makes circuit...when smoke, alpha can't ionise air...no current...breaks circuit...sounds alarm |
| What happens to uranium when found in substances such as granite? | It goes through a series of decays, eventually forming a stable isotope of lead |
| How can you find the approximate age of a rock containing uranium? | By comparing the amounts of uranium and lead in the rock |
| How does comparing the two elements help? | Because the proportion of lead increases as time increases. If there are equal quantities of lead and uranium then the rock is one half life (of uranium) (4500 million years) old |
| What is the radioactive isotope that is present in all living things? | Carbon-14 |
| What does measuring the amount of carbon-14 in an archaeological find tell us? | Its approximate age |
| Describe the process of using carbon dating to find a sample's age | Object dies...no more carbon-14 produced...carbon-14 decays...activity of sample decreases...ratio of current activity of living matter compared to sample activity gives age |
| Why is alpha not useful for diagnosis or therapy? | Because it is very ionising and is absorbed by the skin |
| Why can beta radiation be used to treat eyes but not the rest of the body? | Because it can only pass through skin and not bone |
| Why is gamma radiation (such as Cobalt-60) good for treating cancers? | Because it is very penetrating |
| Why is ionisation not good for people? | Because it damages living cells, increasing the risk of cancer |
| What is radiotherapy? | Radiotherapy is where cancer cells in the body are destroyed using large amounts of radiation |
| How can materials be made radioactive? | When their nuclei absorb extra neutrons in a nuclear reactor |
| What happens when someone has an x-ray? | The tissues absorb some of the ionising radiation-amount absorbed depends on thickness and density of material |
| How are gamma and x rays different/similar? | Difference-made differently Similar-wavelengths |
| How are x-rays made? | By firing high-speed electrons at metal targets |
| Why is making x-rays easier than making gamma rays? | Because the rate of production and the energy of the x-rays can be controlled, but gamma rays are emitted randomly |
| What does technetium-99m do? | It is a tracer for the body that only emits gamma radiation |
| What is the tracer Iodine-123 commonly used for? | It emits gamma radiation to investigate the thyroid gland |
| How do we use tracers to investigate different parts of the body? | Radioactive tracer eaten/drank/injected...tracked using detector hooked up to a computer |
| How are tumours destroyed? | Using a radioisotope |
| How are radioisotopes used to destroy a tumour? | Applied at three points around area...healthy tissue only receives third of dose...reduces damage OR radiation source slowly rotated around tumour...tumour=constant rad...healthy tissue=intermittent doses |
| What are the two isotopes found in uranium? | uranium-235 and uranium-238 |
| What is different between uranium and 'enriched' uranium? | 'Enriched uranium' is used as a fuel and contains more uranium-235 than usual |
| When does fission occur? | When a large unstable nucleus is split up and energy is released as heat |
| How does fission produce electricity? | The heat from fission boils water...producing steam...makes turbine blades turn...turbine turns generator...produces electricity |
| What is a nuclear bomb an example of? | A chain reaction that hasn't been controlled |
| How does the chain reaction of fission occur? | Atoms of uranium-235 are hit with neutrons causing the nucleus to split, producing energy |
| What two elements are normally made when the fission of uranium-235 occurs? | Krypton and barium |
| How is the chain reaction continued? | The extra neutrons emitted cause further uranium nuclei to split |
| How does a graphite moderator help control nuclear fission? | It slows down the fast moving neutrons emitted, these are more likely to be captured by other uranium nuclei |
| How do boron control rods help control nuclear fission? | They can be raised/lowered and absorb neutrons |
| When does nuclear fusion occur? | When two light nuclei fuse together releasing large amounts of heat energy |
| Why does fusions use for large-scale power generation remain a dream? | Because it requires extremely high temperatures which are almost impossible to recreate on earth |
| How do they keep down the costs of research into fusion? | By creating an international joint venture (sharing costs, expertise and benefits) |
| Name an example of when nuclear fusion takes place | In stars |
| How do fusion bombs work? | Started with fission reaction, creating exceptionally high temperatures |
| What are the problems with carrying out fusion on earth? | Getting the high temperatures...solving safety and practical issues...cold fusion not accepted as realistic (results impossible to verify) |
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