electricity

• kirchoff laws for series circuits:

  • current is the same everywhere
  • sum of total pd = sum of emf
• kirchoff laws for parallel circuit:

  • sum of current entering junction = sum of current leaving junction
  • pd is same across each branch
• things that affect resistance

  temperature, material, cross sectional area, length
• resistivity:

  what resistance would be in a material of length 1 and cross sectional area 1
• superconductors

  no resistance when temperature is below critical temperature, which is usually very low - 0k
• uses of superconductors:

  • power cables - reduces energy lost as heat from friction
  • strong magnetic fields, e.g maglev trains
• emf

  the energy transferred by a cell per coulomb of charge (chemical to electric)
• terminal pd

  pd across terminals of cell - available to circuit after lost volts
• lost volts

  voltage lost due to internal resistance
• internal resistance

  caused by electrons colliding with atoms in battery, causing energy to be lost inside the battery
• mains electricity is 230, what V is this?


  V rms