Unit 1 Flashcards
What is an field?
A region of space where an object will experience a force without being touched
Where do electric fields exist?
Around charged particles and between parallel charged plates
In what direction do electric fields always point?
Positive to negative
For electric fields between parallel plates, field lines must:
Point from + to -
Be parallel and at right angles to the plates
Be equally spaced
Touch the plates
End bits usually ignored
How do electric fields work?
Each particle experiences an unbalanced force due to the electric field and so it will accelerate
What is the same as work energy?
Kinetic energy
What is potential difference?
The work energy gained by 1C of charge (due to an electric field)
What produces a magnetic field?
Moving charges or a flow of charges
What experiences a force in a magnetic field?
Moving charged particles
Right hand rule
For electrons
thumb-thrust
index-field
middle-electron flow (original)
Three main parts of particle accelerators
Electric fields-used to accelerate the particles across a potential difference (work done=QV=gain in kinetic energy)
Magnetic fields-used to change the direction of (or deflect) the charged particles
Collision chambers and detectors-where high energy collisions of charged particles take place to produce other particles which can be studied
Three types of particle accelerators
Linear accelerators
Cyclotron
Synchrotron
what is not needed in a Linear Accelerator?
No magnetic field needed as particles are accelerated in a straight line across more than one voltage
Linear accelerator- Why is it important that an ac supply is used?
To keep the particles accelerating in the correct direction. This is done by keeping the electric fields in the correct direction
Linear accelerators- Why do the ‘drift tubes’ get longer?
Because the particles keep getting faster so they can travel further in the same time. The time is the same to ensure they stay in sync with the alternating supply.
Cyclotrons-what fields?
Use both magnetic and electric fields to accelerate particles
When it reaches the outer edge of the cyclotron the particle beam is extracted and used in other experiments such as collisions
Cyclotron - why is an ac power supply used?
as the direction the particle enters the accelerating gap changes, the electric field also needs to change so it is always pointing in the correct direction to accelerate the particle
How do synchrotrons work?
They use a magnetic field which gets stronger as the particles get faster, allowing the radius of the path to stay constant
They have accelerating cavities at many different points around the ring to increase the speed of the particles they go around
What are the two main groups of fundamental particles?
Fermions
Bosons
What are Fermions?
Particles of matter
Eg quarks and leptons (fundamental particles)
(hadrons)
quarks-up, down, strange, charm, top, bottom
leptons-electron, muon and tau, together with their neutrinos
How was the existence of quarks proved?
By high-energy collisions between electrons and nucleons (neutrons and protons) in particle accelerators
What are bosons?
Force exchange particles
examples of bosons
Photon-carrier of electromagnetic force
Gluon-carrier of strong nuclear force
W boson-carrier of the weak nuclear force (can have - or + charge: antiparticles of each other)
Z boson-carrier of the weak nuclear force (has no charge - is its own particle)
What are Hadrons?
composite particles made of quarks?
Examples of hadrons
Baryon-3 quarks or 3 antiquarks
Mesons-made of a quark and antiquark
Anti matter
Each particle in the standard model has a corresponding anti-particle
Identical in every way apart from electric charge
Bar above symbol
How do we know anti particles exist?
When a particle and its antiparticle meet they perfectly annihilate each other
Their combined mass is converted into energy
The energy produced from the annihilation is our evidence for the existence of antimatter
What was the first evidence for the neutrino?
Beta decay
when a nucleus decays in beta minus decay, an anti-electron neutrino is also given out alongside the electron
1ev=
1.6x10^-19J (energy an electron gains when accelerated through 1V
W=QV
Isotopes
Atoms of the same element but with a different number of neutrons in the nucleus
examples of elements which can undergo spontaneous fission
Plutonium 239
Uranium 235