How can a fridge magnet cling against gravity endlessly without a power source ?

Question

It certainly takes tremendous energy to cling endlessly to the fridge by magnetic energy.

Science tells us, such an expenditure of energy requires that a power source be drawn upon to support such effort. there isn’t a power source in sight!

Answer 1

Michael Martin Nieto, a theoretical physicist at Los

Alamos National Laboratory in New Mexico says.

"Everything about gravity is mysterious"

Einstein was so dissatisfied with our lack of understanding

about gravity even two centuries after Newton that he invented an entirely new theory of gravity, yet this theory doesn’t solve these problems either.

You can take all the courses you want but it won't change the fact that gravity and magnetism are mystifying the largest brains.

You all need to say, interesting point, Here is my take, but basically I don't know. No one knows.

Good question.

Answer 2

Magnetic force and electrical forces are interchangeable. If you were to drop a magnet through an aluminum tube, it would create an electrical field which could counter the gravitational pull, and magnets aren't even attracted to alluminum.

For that matter what powers gravity? Why does gravity not eventually run out of power? Perhaps one day the earth gravitational field will fail and we will float off into space.

This will never happen, nor will the magnet stop sticking to the fridge.

Answer 3

magnet. it is like glue. i think.. i am just 11 years old...

Answer 4

I have nothing to add that could improve upon TR's answer.

Answer 5

Friction. The magnet holds itself against the surface with enough force so that frictional force is as strong as the gravitational force. The typical refrigerator magnet has a lot of surface area, so it doesn't have to be that strong.

Now, the answer to why no power source is needed is this: In general, forces simply do not require a power source.

For example, blow up a ballon. If you press against the balloon with a finger, it pushes back. Does the balloon have a power source?

There are ways of generating force by expending energy, but they are generally require energy because they involve moving things.

For example, you could make an electrical device that can cause an object to float in the air 6 feet above the floor. It would take energy because moving electrons generates the force and it takes energy to move electrons. You could also simply hang the object from the ceiling or put the object on a shelf. Neither of those require any energy at all (other than moving the object to the correct height) because nothing is moving.

Answer 6

JohnB is quite right. Work, by definition, is the action of a force moving through a distance. The work equation is applicable to any scenario, anywhere, whether the object of interest is moving or not. If this weren't the case, the work equation would be absolutely useless (and wrong as well!) So by that definition, a magnet sticking on the fridge is doing no work. Energy is likewise defined as the ability to do work, so if no work is required, therefore no energy is either. This is fundamental physics from the law of conservation of energy. Science does not, in fact, tell us there has to be a power source to draw upon, since no energy consumption is occurring.

Theoretically, a permanent magnet isn't actually that permanent. If given enough time, in theory, quantum effects will destroy the long range ordering giving the magnet its magnetic properties. We're talking millions of years here at room temperatures. But you can remove the magnetism nearly instantly by heating it above its Curie point.

If you haven't taken coursework in physics, these concepts can be very confusing, especially since energy and work have physical definitions that are somewhat different than the layman's understanding of the terms.

EDIT: Kristy, the difference between a force applied by a permanent magnet and a force applied by a muscle is that a constant muscle tension requires a constant input of energy, while a permanent magnet does not. Perhaps a better analogy here is that a muscle is like an electromagnet -- both require a constant power input to maintain force. For an electromagnet, that power goes into atomic ordering. A permanent magnet already has permanent long-range ordering, so no power input is needed to generate magnetic force.

You might be surprised to learn that the guy hanging on the cliff isn't doing any external work! That's counter-intuitive, but here's why: there is certainly biochemical work going on inside his body (internal work) to maintain muscle tension in his hands (which makes  him tired), but since his body is not moving, he is not doing any work on his body (external work). By the same reasoning, a magnet isn't doing any external work if it is not moving, and since the permanent magnet does not require internal work to maintain its atomic ordering, no internal work is done either. Therefore, no energy is being consumed.

If you don't understand the physical definition of work, you won't understand why the above is true. I attached a new link from Dr. Simanek at UPenn which delves into this a little bit. It's pretty relevant. YA is a poor forum for teaching these kind of things, but perhaps you can contact him for more help.

Again, I'd highly recommend taking a physics course maybe at your local community college. You might find it more enlightening to first learn about physics before you become a critic of it :)  And yes, the bottom line here is friction. Friction force holds the magnet. The Normal force contributing to the friction force is caused by the magnetic pull of the magnet.