physics paper 1

• in a series curcit if you remove one the whole curcit will be broken
• in a parrell curcit all the components are seprerate so if one is removed it will not chage the curcit
• in a seireis curcit all the resistors add up
• in a parrell curcit adding more resistors reduces the total resistance
• investigating resistance

  have no resistance and calculate it and then add it gradually repeat 4 to 5 times
• in the home the live wire is brown it has a alternating current and a pd of 230
• in the home the nuetral wire is blue the complets curcit and has a pd of 0
• in the home the earth wire is green and yellow it is a saftey wire and only carries a current when somthing is wrong in the curcit
• the natinal grid transfers elecrtic through cabels and transformers
• the natinal grid uses a high pd and a low current bevause if there was more current more would be lost through wasted enrgy
• the build up of static is caused by friction
• when insuating matirals are rubbed together negitivly charged electrons will rub off onto one another and leave it electrally charged
• consevation of energy is that energy can be transfered usfully stored or dissipated but can never be created or destroyed
• conduction is the transfer of energy from one molecule to another by vibrations
• convection is partiles moving away from hotter to coller regions
• an exapmle of convection is a radiator by the hot air rising and the cool air sinking and going back into the raaidiator
• john dalton said the matter was ting sphers that cannot be broken up but each element was diffrent
• jj thompson discovered electrons and the element was positivly chrgered plum puddin model
• ruthuford-gold foil experiment staid that it was mainly empty space so that was the nuculas that ment that electrons orbit it
• james cadwich proved evidence which explained the imbalence between atomic mass and mass number
• fissioin is the splitting of a unstable nuculas it is spontanous and raley happens after one or two has happend this will cause a chain reaction this is used in nucular wepons
• lubraction reduces frictinal forces so no energy is wasted
• an insulator is cavity walls they have and inner and outer layer to create a vacum so room will be hotter for longer
• energy can be transfered by: heating, light, sound, electricity, chemical reactions
• isotopes are atoms of the same element with different numbers of neutrons and same number of protons
• unstable isotopes tend to decay into other elements giving out radition so try and become more stable
• alpha particles will penertate through paper and can only travel a few cm in the air they are very strongly ionising
• beta particles can be stopped by a few millimetres of aluminium and only travel a few metres in the air they are moderatly ionising
• gamma rays can be stopped by a piece of thick lead they are weakly ionising so is used in things like medical scans
• internal energy is the total energy in kenetic and potnetail
• change of state is a physical change has same number off particals but are arranged diffrently
• when changing state the temp will rize until it stops to break the bonds
• specific latent heat is enegry needed for 1kg of mass to chage state
• as gasses particles collide more which increases the pressure which increases temp which will increase pressure
• units

  v=volume(m3)

  pressure =pascals(pa)

  joules=energy(J)

  mass=kg

  specific latent heat (j/kg)

  density=kg/m3

  power=W

  p.d=V

  current=A

  time=s

  resistance=ohms

  work done=J

  height=M
• solids have strong forces of attraction and can only vibrate and have a density
• gases have no forces between them and are freely movable and have a low density
• finding density of a solid

  use a balence the measure the weight

  measure length width hieght and calculate volume(if regular)

  (if irregular)place object in uretha beaker and measure the volume of water that came out

  calculate the density
• finding density of liquid

  turn balence to 0

  pour 10 ml and record the mass then calculate the volume

  density(1ml=1cm3)

  find average density
• factors affecting resistance

  attach crocidile clip to wire at 0cm

  attach second clip 10 cm away

  close switch and record current and p.d

  move 10cm more every time and repeat