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Magnet and gree energy

  1. Jul 13, 2004 #1
    magnet and free energy

    when i stick a magnet on a fridge it willl eventually slide down and fall of due the domains in the mganet nuetralizing each other out right ?

    Now my question is does the energy reuiqred to realign the the magnet to its original strength = the amount of enrgy that is requireed to keep that magnet against the fridge working against gravity for the length of time unitll it falls off

    seems like more energy to keep magnet on fridge thatn to realign it
     
    Last edited: Jul 13, 2004
  2. jcsd
  3. Jul 13, 2004 #2

    Gza

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    Conservation of energy would deem your assumption false.
     
  4. Jul 13, 2004 #3

    krab

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    Science Advisor

    That amount is zero. A constant force does not imply an expenditure of energy.
     
  5. Jul 13, 2004 #4
    im confused if I physically hold the magnet that fell off ; agaisnt the fridge myself instead of magnetizing it am I not expending energy
     
    Last edited: Jul 13, 2004
  6. Jul 13, 2004 #5

    Gza

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    Energy changes in a physical system are caused by work. Work is defined as a force over a distance. If you hold a magnet in place without moving it, there is no possible way work can be done, therefore no expenditure, or for that matter, absorption of energy.
     
  7. Jul 13, 2004 #6

    russ_watters

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    Staff: Mentor

    Your body expends energy doing anything. But you are not imparting any energy onto the magnet by holding it against the fridge.
     
  8. Jul 13, 2004 #7
    ok understand now
     
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