Sparks & Fission - Questions
- What happens when two acetate rods are brought near each other?
- What happens when a polythene and a acetate rod are brought near each other?
- Why does an acetate rod become positively charged when rubbed with a duster?
- Suggest how tumble drier sheets can reduce static "cling" in your clothes.
- What is meant my "enriched uranium" ?
- How does a chain reaction enable a large amount of energy to be produced in the fission of uranium?
- Why is radioactive waste dangerous?
- What do the control rods in a nuclear reactor?
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Sparks & Fission - Answers
- They repel
- They attract
- Electrons move from the acetate rod to the duster.
- The sheets contain oil so they reduce friction; they are made from conducting material so no charge can build up.
- Uranium contains a greater proportion of the uranium-235 isotope than occurs naturally.
- Extra neutrons are released which split more uranium nuclei producing more neutrons and so on.
- It emits harmful ionising radiation for a long time.
- They absorb some of the neutrons to control the number of fissions occurring.
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Uses of Electrostatics & Safe Electricals - Questi
Uses of electrostatics
- Suggest why a defibrillator must be placed firmly on a patient.
- A defibrillator has a power rating of 100,000W. For how long must it be switched on to provide 500J of energy?
- Ali is spray painting the frame of his bike. Suggest why he will get a better finish if the earths the frame.
- Why do the wired in an electrostatic dust precipitator need to be at a high voltage?
- The pd across a resistor is 4V when the current through is 0.5A. What is its resistance?
- Calculate the current in a 10 resistor when the pd across it is 4V.
- Explain how a fuse protects an appliance.
- How does an earth wire stop a person getting an electric shock?
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Uses of Electrostatics & Safe Electricals - Answer
Uses of Electrostatics
- To ensure good electrical contact.
- Electrons flow to or from earth to keep the frame uncharged giving a more even coverage; there is less water; shadows are painted.
- To charge the soot particles when they come near the wires.
- Wire in a fuse melts if the current becomes too large, breaking the circuit and preventing overheating.
- It is connected to the case of an appliance so that if the case becomes "live," a large current flows in the earth and live wires and the fuse "blows."
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Ultrasound & Treatment - Questions
- Body fat is denser than air. In which will ultrasound travel faster?
- Is a Mexican wave a longitudinal or a transverse wave?
- An ultrasound pulse travels 20cm further when it is reflected from one side of the head to the other. How big is the head?
- The time delay for an ultrasound echo in a soft tissue was 0.0004S. At what depth was it reflected if the speed of ultrasound is 1200M/S?
- What is "radiotherapy"?
- Give two similarities and two differences between x-rays and gamma rays
- Why is iodine-123 used as a tracer in medicine?
- Explain why gamma radiation is often directed at a tumour from different directions.
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Ultrasound & Treatment - Answers
- Body Fat
- Using radiation to treat diseases such as cancer.
- Both electromagnetic radiation; both have very small wavelength; both very penetrative; both damage or kill living cells.
- Iodine is taken up by the throid gland and it emits only gamma radiation.
- So that the tumour receives the full does of radiation but healthy tissue receives less radiation.
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What is radioactivity? & Uses of radioisotopes - Q
What is Radioactivity?
- Three successive measurements of a radioactive source are different, why?
- The activity of a radioactive sample took 8 hours to decrease from 5000Bq to 1250Bq. What is its half-life?
Uses of Radioisotopes
- Why can't carbon dating be used to find the age of an iron tool?
- Why must a gamma source be used as a tracer rather than alpha or beta?
- Why would you expect a new rock to contain a bigger proportion of uranium to lead than an old rock?
- The half life of carbon-14 is 5600 years. Why can't it be used to date an object believed to be about 100 years old?
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What is radioactivity? & Uses of radioisotopes - A
What is radioactivity?
- Radioactive decay is a random process.
- 4 hours.
Uses of radio isotopes
- Iron was never living so does not contain any carbon-14
- Only gamma radiation will penetrate through pipes, ground. etc.
- Less uranium has decayed to lead.
- Very little carbon-14 would have decayed so there would be very little change in activity.
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