# A motor can work without a magnet

## Why not a perpetual motion machine through magnetic force?

You hold postcards on the wall of the refrigerator and let doors close securely ... There is something magical about the power of magnets: as if by magic, opposing poles attract each other, while the same poles repel each other. Why can't these effects be used to generate an inexhaustible source of energy? Sebastian W. made us aware of this topic - thank you very much!

The explanation is provided by Alois Loidl from the Chair of Experimental Physics V at the University of Augsburg: “Magnets can indeed do work through attraction or repulsion, but that is exactly what you have to use to separate or bring them closer. This is why this system cannot be converted into a cycle that continuously supplies energy, ”explains Loidl.

### Energy yield - no news

The famous perpetual motion machine cannot conjure up magnets either. It is a fictional construction that once started, remains in motion forever and does work without having to be supplied with external energy. Unfortunately, this dream of generating energy remains a fiction because it contradicts the law of conservation of energy: the total energy of a closed system does not change.

"In order to create a permanent magnet, you first have to put energy into it," emphasizes Loidl. Magnetizable substances consist of many small magnetic particles, the elementary magnets. Usually their orientation is disordered, like many tiny compass needles pointing in different directions. The magnetic fields cancel each other out and there is no magnetic effect. For the production of a permanent magnet, the particles of a magnet must therefore be rectified using energy. This happens in a strong electromagnetic field that is generated by electricity. “This work of magnetization then remains in the magnet, so to speak,” says Loidl.

With its magnetic force, the permanent magnet can then attract other ferromagnetic substances. "In doing so, he does work, but that is exactly what you have to spend again to bring about a separation against the force," says Loidl. The energy balance therefore remains at zero - unfortunately no energy can be obtained from the system.

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© Wissenschaft.de - Martin Vieweg / dapd
April 22, 2017