magnets are a free source of energy (potential energy from attraction or retraction) that lasts forever, couldnt magnets be used to generate energy for example to power a car?

How do magnets work and why are they able to repel and attract only certain metals, but not others?

Iron will attract magnetic lines of force by making their path through the space easier.  Is there any material which will prevent or block the passage of those lines of force?

Using a magnetic building toy, I took two balls and attached one magnetic rod to one and four to the other, all with their north poles pointing to the balls. Although it seems that the balls should repel, one can in fact suspend one from the other! The effect is diminished if I reverse one or two of the four magnets attached to the second ball. The balls do in fact repel if I place only one magnet on each ball or if I have four magnets on each ball.

A family member recently bought her dog (working class bearded collie)  Norstar "biomagnetic dog collar" which supposedly "increases energy, brings relief to pain and generally improves health and well being".

I have also seen similar items in sports magazines for use on people with similar effects.

My question is how do these items work, that is if they actually produce an effect on people/animals

When a magnet lifts a metallic object against gravity, it is doing work and energy is being converted. Where does this energy come from? Presumably it comes from the magnet- but what form does it take and does it eventually get depleted- or - is the energy restored as the metallic object is pulled away from the magnet?

Thanks

Steve Fletcher

Simon Galloway

Andy Carter

Anaesthetic Dept

Bradford Teaching Hospitals

In my local store there is an interesting drink advertisement; a machine with two circular discs, one at the bottom and one at the top, seems to make a can of drink levitate and rotate so that customers can see the whole label. I think the machine uses electromagnets to do this, but I am still curious about it because the can never moves vertically - only slightly horizontally, and forwards and backwards. I tried removing the can once and the can didn't float when I replaced it. How does this work and how does the machine achieve such a precise region of movement for the can?