# Shared Flashcard Set

## Details

A Level Physics
Particle Physics and Electricity
31
Physics
Not Applicable
12/01/2016

Term
 Capacitors: Charging
Definition
 Electrons move around circuit from one plate to the other until the PD across the capacitor = the supply PD
Term
 Circular motion: weightlessness
Definition
 You feel weightless when the reaction force = 0 - so going over a humpback bridge or over a vertical loop, at the top, mg=mv2/r
Term
 Elastic collisions
Definition
 Kinetic energy conserved
Term
 Electric Field: Uniform Field
Definition
 Region where a force acts on a charged particleThe force is the same at all points
Term
 Emission of electrons
Definition
 Cathode is heated (by a current)causing Thermionic emission
Term
 Faraday: Peak in voltage when a current in a coil is turned off: Faraday's Law
Definition
 Current in coil Generates a magnetic fieldturning off current causes a rapid change in fluxInducing a large emf
Term
 Faraday: Why you get a large emf
Definition
 Lots of coils means large flux linkage
Term
 High-Energy particles
Definition
 Particle is moving fast - mass will be larger due to moving near the speed of light
Term
 Induction: Magnet not moving
Definition
 Magnetic field from electromagnet changes (due to AC current)Flux through coil/wire changesInduces EMF
Term
 Induction: Moving magnet
Definition
 Magnet movesFlux through coil/wire changesInduces EMF
Term
 Lenz's Law: Minus
Definition
 induced current/emf (direction)Opposes the change (that produced it)
Term
 Mass conversions
Definition
 Gev/c2 to kg: Simply convert the eV to Joules (1eV=1.6x10-19J) and then divide by c2 (because mass=E/c2)
Term
 Momentum: Particles leave at right angles if they've the same mass
Definition
 Use pythagoras
Term
 Momentum: Rocket propulsion
Definition
 Momentum conservationTotal/initial momentum = 0Momentum of material ejected equal momentum of rocketRocket moves in opposite direction
Term
 Motor Effect
Definition
 Current in a wire creates a magnetic fieldMagnetic field is around wire.If this interacts with another magnetic field there will be a force - Fleming's LHR gives direction of force
Term
 Particle Accelerators - size of force
Definition
 Electric field applies a force to the charged particle (proton) as F=Eq
Term
 Particle accelerators :Steering Particles (cyclotron)
Definition
 E-Field: Provides force (as F=Eq) to accelerate the charges across gap between DeesB-Field: Provides a centripetal force on the charge to move it in a curveThe E-Field reverses each time the charge enters a Dee
Term
 Particle Detectors : Why a magnetic Field?
Definition
 To provide a centripetal force to cause the particles to travel in curved paths.…so that you can investigate their momentum/mass/KE
Term
 Particle Detectors: B-Fields
Definition
 • provides a centripetal force • Direction of force/curvature/deflection indicates (sign of) charge.• momentum/speed/mass found from radius/curvature• r = p/BQ Or Bqv = mv2/r
Term
 Particle Detectors: E-Fields
Definition
 • can be used to accelerate or deflect particles• direction of force (deflection)indicates (sign of) charge.• a = EQ/m
Term
 Particle Tracks - uncharged particles
Definition
 Uncharged particles leave no tracksThe decay of an uncharged particle will be see as two or more tracks appearing from "nowhere"
Term
 Particle Tracks: Conservation
Definition
 Curve in opposite directions: charge conservedTwo tracks appearing: charge conserved (initial particle, charge=0 - new particles +1 + -1 = 0)Particles moving in opposite directions: conservation of momentum(depending on context)
Term
 Particle tracks: Curvature
Definition
 The radius of curvature gets less as it slows down
Term
 Particle Tracks: Curves
Definition
 More curved, particle is slowing as it loses energy.
Term
 Particle Tracks: Vacuums
Definition
 A vacuum so that the particle does not collide with gas molecules
Term
 Particles :Antimatter
Definition
 Same mass, opposite charge, lepton number, baryon number (Can be stored in an electric field if the particle is charged)
Term
 Particles :steering
Definition
 Force acts at right angles to direction of ion movementThis force provides a centripetal force
Term
 Particles Decay: Conservation of properties
Definition
 Momentum conservedCharge conservedEnergy / mass conservedBaryon Number/Lepton Number
Term
 Particles: Conservation of Momentum
Definition
 When a particle decays particles leave in all directions because * initial momentum is zero * so sum of momentum of fragments = zero to conserve momentum
Term
 Rutherford's Experiment
Definition
 ObservationsMost alpha went straight throughSome deflectedVery few came straight backConclusionsAtom mainly (empty) spaceNucleus contains most of the mass Nucleus very small Nucleus positively charged
Term
 Vector Diagrams
Definition
 Draw the vectors "Nose-to-tail" - the resultant vector is the vector from the start of the first to the end of the last
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