Electric Current

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  • Created by: Murray_R
  • Created on: 15-12-13 17:56

Current & Charge

  • Current= flow of electrons (I)
  • in metals the charge carries are conducting electrons the move around in the metal colliding with each other and fixed ions
  • in salts the charged is carried by ions

   Q=I  t


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Potential Difference & Power

  • P.D or Voltage=the work done per unit charge

    V=W/Q

  • The emf of a source of electricity is defined as the electrical energy produced per unit charge passing throught the source

W(work done)=IV  t
power=IV

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Resistance

  • Resistance= the pd of a component /the current through it

R=V/I

  • an ammeter is used to measure current and is connecred in seris
  • a voltmeter is used to measure the PD and is connected in parralel to the resistor
  • a variable resistor can be used to adjust the current and P.D
  • Ohms law stated that the pd across a metallic conducto is proportianal to the curren through ***, providing the physical condition does not change
  • on a graph where voltage (y) is plotted against current (x) the resistance isthe gradient

Resistivity(   )=RA/L
r=d/2, a= Πr2

  • Superconductivity=a wire or deice made of a material which has zero resistance at and below a critical temperature( this depends on the material) if the temperatire is raised then the superconductivity is lost the boiling point of liquid nitrogen is called a high-temperature superconductor, superconductours are used to make high-power electromagnets that generate strong magnetic fields without waisting energy

 

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Components and there charicteristics

  • Tempratue= resistance increases with temperature as positive ions vibrate moe which makes it harder for the current to pass it is called Positive temperatue coefficent
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