Law of conservation of energy. Flawed?

Question

Consider holding a large magnet. now move the magent closer to a small piece of iron. When you get closer, the magnet attracts the iron. This attraction moves the iron to the magnet. This movement produces WORK since Work = force x distance. This work expends energy. Does it mean that the magnet "looses" some of its energy? Will after so many tries, we will exhaust all the magnetic properties of the magnet?

This is just some thing that made me think.

Answer 1

The work done on the iron comes from the potential energy of the iron. Because it is separated from the magnet, the iron starts out in your experiment with magnetic potential energy. Just like a block of iron held above the floor has gravitational potential energy. When the force is large enough to overcome friction with the table, the magnetic potential energy gets converted into kinetic energy.

Answer 2

Your talking about 2 different types of "force' here electromagnetic and gravity. The electromagnetic is obvious in this query but maybe not so much gravity. Gravity pulls the iron object to the table, when the iron object scoots across the table it has to overcome friction caused by the gravity.

If these 2 forces are balanced there is no movement that's why you have to move the magnet closer because it's force (as well as gravity's) is governed by the inverse square law which is 1/d^2. Meaning if you move the magnet 2 units away from the object the force the other object "feels" is 1/4 it did when it was closer. Move it 4 units away and the force is 1/16. And so and so on, but that's another topic.
The conservation is the electromagnetic force overcoming the force of friction caused by gravity which produces heat which is energy. Although you don't see it, energy is being conserved via heat caused by friction

Magnets do not loose there power because of use. They lose their force do to distance as mentioned above. Only on the short term though. The magnet still has the same force with the bar attatched to it but when you attatch another bar to the bar already attatched the force is less because it is further away from the magnet. Try sticking a magnet into a box of screws and you'll notice a taper effect. Bunch of screws up top and one screw barely hanging on at the bottom. This is because of distance.

Heat and sharp blows change a magnets force. Otherwise it's magnetism will remain about the same indefinitely.

Answer 3

Every time the magnet draws the piece of iron towards it, it is doing work on the iron. However, every time you pull the iron away again, you are doing an equal amount of negative work. The net work done on the iron after each cycle is zero. The work done on the magnet, which doesn't move, is also zero.

Energy is conserved.

Answer 4

The magnetic force is created with the force of electrons, that is when they move in a single direction, this force can never be over.
Another Example:
Earth's Gravity...It is a force, but never ends

Answer 5

it doesnt looses energy because the law of conservation say that the energy becomes something else what is known as a photon. The frequencies of the electrons may change but never loose its energy; that energy becomes a photon

Answer 6

hi the point wher u r makin a mistake is that there is no work done as magnetic lines of forces are perpendicular to the direction of propagation of the iron.so no work no energy nothin
just a guess might be rong

Answer 7

see from the magnets reference frame the nail is approaching it let it be x distance
and from the nails reference point magnet is approaching it and it will be -x
thus

x-x=0

Answer 8

Thats a great point. I think you should develop this hypothesis a little further and present it wit more information. You never know! You may be winning a nobel prize soon enough!