P4 - Radiation for life

This is about P4 - Radiation for life

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Sparks & Fission - Questions

Sparks

  • 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.

Fission

  • 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

Sparks

  • 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.

Fission

  • 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?

Safe Electricals

  • 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.
  • 5ms
  • 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.

Safe Electricals

  • 8
  • 0.4A
  • 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

Ultrasound

  • 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?

Treatment

  • 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

Ultrasound

  • Body Fat
  • Transverse
  • 10Cm
  • 0.24M

Treatment

  • 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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