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Magnets attract and oppose, right?

  1. Oct 25, 2011 #1
    then why has no one built an engine that requires no wires, no copper. no batteries, capacitors, resistors, no electricity whatsoever? if a magnet is strong enough it can push or pull something, right? then why aren't wheels magnetic? generators, engines, rotors, hard drives....why is electricity necessary if magnetic fields already make things move?
     
  2. jcsd
  3. Oct 25, 2011 #2
    Because magnets are not power sources. You're converting potential energy to kinetic energy and vise versa.

    Think of the repelling force of a magnet as a balloon on a stick (because that's really what it acts like). You can push against the balloon and get it to push back, but it's only because of the force you initially put into it.

    Think of the attracting force as just gravity. You can climb up onto a chair and jump off and yes gravity will pull you down, but without using energy for your initial effort of climbing onto the chair you wouldn't have been able to get that conversion of gravitational potential energy into kenetic energy moving you downwards.

    Now if we put these forces together to try for perpetual motion we get something like you dropping a ball onto a trampoline, sure you will get an oscillation (the bouncing of the ball) for a period of time but eventually it will find equilibrium and movement will come to a stop.
     
    Last edited: Oct 25, 2011
  4. Oct 25, 2011 #3

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    Perpetual motion machines are on the PF "Banned Topics" list, as described in the Rules link at the top of the page. You can read through the linked, locked threads quoted below for more information on why PMMs are not possible.

     
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