P2- current electricity

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electrical charges

  • two insulating material rubbed together= electrons rubbed off one and deposited on the other
  • electrons have negative charge so material gaining the electrons becomes negatively charged, the object which has lost the electrons becomes positively charged
  • on a polythene rod the electrons are gained so it becomes negative and the cloth becomes positive as it looses the electrons
  • this process is called charging by fricition
  • two objects with opposite charge= attract
  • two objects with same charge= repel
  • bigger distance between two objects= smaller force

electric circuit

  • current= charge/ time
  • (http://physicsnet.co.uk/wp-content/uploads/2010/06/circuit-symbols1.jpg)

resistance

  • current(amps) through a circuit measured by an ammeter
  • ammeters always placed in series component
  • the potential difference(volts) of a component measured by a voltmeter
  • voltmeter is always placed in parallel with component
  • potential difference= work done/ charge (columbs)
  • resistance is the opposition to current flow
  • resistance(ohms)= pd/current
  • ohms law= if a resistor is kept at constant temp the current potental difference graph shows a straight line passing through origin…

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