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Physics Paper 1 (Electric and Magnetic Fields (Transformers (Flemings…

- - - - B= Magnetic field strength (better known as magnetic flux density (the amount of field lines in a given area, measured in tesla)
      - Magnetic fields are vector quantities, and hence they have a size and a direction, and can have vertical and horizontal components
  - - - C= e0*A/D when there is only air between the two plates
      - is there is material between the two plates C=(ere0) A/D
      - A= common area of the two plates, d = the separation between the two plates, er is the relative permittivity, and e0 is the permitttivity of free space
    - - RC = the time constant for the circuit
      - The time for Q, V and I to fall to half their original values is RC*ln2 (ln 2 = approx. 0.69)
  - - - E= -N dphi/dt phi= magnetic flux t= time N= number of turns in a coil of wire e= induced emf
      - Phi = BA (flux density * area)
  - - - Thumb = motion, first finger = field, second finger = current
- - - - A voltage drop means that the charge has lost energy
      - An e.m.f (electromotive force) means the charge has been supplied with energy
      - Example is a cell- which has a surplus of electronis at the negative end, and a lack of them in the positive terminal
        
        The potential difference is the measure of the "push" they recieve over a set distance,
        
        The electrons will lose voltage as they move to fill the positive end of the cell
        
        Electrons require energy to move from one end to another, and so energy is used (conservation of energy) and the voltage at that point frops
  - - - Lamps rely on electric current heating up the filament held within the bulb
        
        There is enough resistance within the filament that the current that passes through it loses enough energy that the filament heats up to a point where it starts to glow from the heat passing through it.
      - Heaters rely on the high resistance of the heater - where the energy lost to the surroundings , and heats up the surroundingair.
  - - - Sum of currents flowing in = sum of currents flowing out
      - Conservation of charge
    - - Conservation of energy
      - Sum of pd.'s across any components in any loop in a circuit must equal the sum of the emf'supplying it.
        
        In other words total emf= IR
  - - - I is proportional to V
      - Hence straight line graph of I=V
    - - Resistance is not constant
      - As current goes up, V/I increases and the resistance therefore gets bigger
      - This is due to the nature of filaments and the fact that they heat up very quickly
      - Can still apply V=IR, but only at agiven voltage and current-i.e. if we double our volaue of voltage the current will increase by less than double.
      - Graph looks a inverse sinusoidal wave
    - - A diode only lets current through when it is flowing in one direction.
      - When the diode is facing the direction of current flow is it is said to be in foward bias.
        
        Even in foward bias it will not conduct until a voltage of around 0.6V (switch on voltage)
      - When the diode opposes the attempted direction of current flow then it is in reverse bias and has a very high (effectively infinite) resistance, allowing no current to flow.
      - Graph looks like exponential
- - - - Equations
        
        v=omegar
        
        a=v^2/r =omega^2 r
        
        F=mv^2/r = m omega^2 r
        
        omega = change in theta/ change in time
        
        omega = 2pif
        
        omega = 2pi/t
        
        f=1/t
      - Centripetal force
        
        is represented by a force within the system, not a separate froce, but it moves the object ina circular motion. in a conical pendulum this force is the tension etc.
    - - p=mv
      - impulse = FxT
        
        impulse = change in m*v = mv-mu
      - F=(mv-mu)/t
  - - - Every action has an equal and opposite reaction on the opposite body
- - - - If the charged particles are negative, then the first drift tube is given positive potential, to accelerate the charged particle
      - Charged particles generated through thermionic emission
      - Inside each tube the particles travel at constant velocity
      - Once the particles leave the first tube, the ac supply will reverse, so the particles are accelerated again
      - The tubes increase in length as the frequency of the ac is constant, so in order to keep the time from one drift tube to another constant, the length is progressively increased, as the velocity of the electron increases, and so the tubes are lenghtened to keep the time they stan in the tube for constant even when they are being accelerated
    - - Consists of two dees, charged particles accelerate from one dee to the next, NOT WITHIN the dee itself
      - magnetic field perpendicular to the dees to keep charged particles in circular motion
      - Time spend in each dee remains constant
        
        This is because the radius of the particle path increases
  - - - same mass, opposite charge, spin and baryon, lepton numbers and strangeness
      - if they collide with normal matter they annihilate each other, and produce two photons (conservation of momentum and energy)
  - - - electron, muon, tau + neutrions and their antiparticles
      - Lightest
      - spin +/- 0.5
      - Acted upon by the weak nuclear force
      - Fundamental particles
      - lepton number +1, anti particles have -1, everything else has 0
    - - Proton is uud, neutron is udd, pion is u anti-d, kaon 0 is d anti-s kaon + is u anti-s and sigma + is u u s
      - Up (+2/3), down(-1/3) strange(-1/3), charm(+2/3) top(+2/3) bottom(-1/3)
      - Experience the strong nuclear force
    - - baryons
        
        Heaviest
        
        spin +/-0.5 or +/- 1.5
        
        made of 3 quarks
        
        Protons and neutrons etc.
        
        only stable baryon is the proton, outside of a nucleus the neutron decays into a proton and an electron and an anti-electron enutrino
      - mesons
        
        masses between leptons and baryons
        
        whole number spin
        
        made of quark and antiquark
        
        very shortlived