Physics P3.4

What are cyclotrons?
Particle accelerators
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What happens to velocity in circular motions?
It is constantly changing, which means it is accelerating
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What acts on the object going through circular motions?
A centripetal force (resultant force), acting towards the centre of the circle
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What happens to a charge particle in an magnetic field?
It has a force act upon it which is perpendicular to its direction of travel
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What does the force on a charged particle in an magnetic field make it do?
It follows a curved track
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What does the direction of force on a charged particle depend on?
It's charge. The positive and negative paths curve in different directions.
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What shape do charged particles create when they are affected by a force?
Spirals. Because the particles lose energy and slow down as they interact with other particles. The less energy the particles have the more curved their path will be
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What are magnetic fields used for?
To make charged particles move in a circular or spiral path in particle accelerators e.g. cyclotrons
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What is a cyclotron?
A circular particle accelerator which uses a magnetic field to accelerate particles to very high energies along circular paths.
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Explain how a cyclotron works
The charged particles start at the centre and the cyclotron uses two hollow semicircular electrodes to accelerate the particles across a gap. An alternating potential difference is applied between the two electrodes and the particles are attracted
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Explain how a cyclotron works pt2
from one side to another and their energy increases because they are accelerating. A magnetic field is used to keep the particles moving in a circular motion and allows them to spiral outwards as their energy increases.
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What does proton enrichment do?
Form isotopes that emit positrons (anti-electrons)
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How are some radioactive isotopes produced?
Bombarding stable elements with protons
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What happens when a proton is absorbed by a nucleus?
It increases the proton number making a new element
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Where does proton enrichment take place?
In a cyclotron as a proton needs a lot of energy to be absorbed into a nucleus
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What are the uses of positron emitters?
PET Scanners to monitor blood flow and metabolism.
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What is the main thing that the radioactive isotopes have to have?
A short half-life so the patients exposure to them are minimised.
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What isotope is used to make fluorine-18 and what it its half life?
Oxygen-18 and just under 2 hours
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What isotope is used to make carbon-11 and what it its half life?
Nitrogen-14 and 20 minutes
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What isotope is used to make Nitrogen-13 and what it its half life?
Oxygen 16 and 10 minutes
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How do you find the radioactive isotopes that are made by regular isotopes?
Add 1 to the regular isotopes atomic number and find that element
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What do scientists use huge particle accelerators for?
To smash particles together at tremendous speeds to see what happens- what kind of radiation is given ff, what particles are created. This gives us clues about how the universe works so scientist have better explanations about the world
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How do the huge particle accelerators get used amongst scientists?
Research is done internationally as particle accelerators are very expensive to make, it uses the expertise of specialists to share ideas. However there can be some rivalry as some scientists will want to be the first to discover something
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Where is the Large Hadron Collider based, who built it, what is it,and what is it used for?
Geneva, CERN, the largest and most powerful particle accelerator ever built, to try and recreate conditions after the big bang by colliding two beams of protons at high speeds.
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Momentum is always...
Conserved
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What can collisions be?
Elastic or Inelastic
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What is an elastic collision?
Momentum and Kinetic Energy is conserved. Some of the kinetic energy is converted into other forms during the collisions
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What is an inelastic collision?
Momentum is conserved but some kinetic energy is lost eg bouncing a ball. This is due to the object having less gravitational potential energy.
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What happens when a particle meets its antiparticle?
Annihilation as all the mass is converted into energy which is given off as gamma rays
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What happens when electrons and positrons meet?
They collide head on at the same speed moving in opposite directions
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What is the total momentum before the collision of electrons and positrons/
Zero as they have the same mass but opposite velocities
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What happens to the gamma rays?
Two are produced with the same energy but opposite velocities
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What is conserved as well as momentum and how?
The charge as it stays at 0. This is because before hand the electron is -1 and the positron is +1 which cancels out. Then gamma rays have no charge.
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What is conserved as well as momentum and charge?
Mass energy. This is because all the mass of the electrons have been conserved into energy. And mass is a form of energy and vice versa.
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Explain how PET Scanning involves electron/positron annihilation.
A positron emitting isotope is injected into a patient. The positrons collide with electrons in the organs causing them to annihilate and emit gamma rays. There will be a higher take-up of radio isotope in tumour cells than normal ones so the
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Card 2

Front

What happens to velocity in circular motions?

Back

It is constantly changing, which means it is accelerating

Card 3

Front

What acts on the object going through circular motions?

Back

Preview of the front of card 3

Card 4

Front

What happens to a charge particle in an magnetic field?

Back

Preview of the front of card 4

Card 5

Front

What does the force on a charged particle in an magnetic field make it do?

Back

Preview of the front of card 5
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