Lenzův zákon
Lenzův zákon (Lenzovo pravidlo) je fyzikální zákon popisující vztah mezi elektrickým proudem a změnou magnetického indukčního toku. Zákon formuloval německý fyzik Heinrich Lenz.
Znění: Indukovaný elektrický proud v uzavřeném obvodu má takový směr, že svým magnetickým polem působí proti změně magnetického indukčního toku, která je jeho příčinou.
Toto pravidlo je důsledkem obecného fyzikálního principu setrvačnosti, tj. snahy k udržení původního stavu soustavy. Zákon se dá odvodit z Faradayova zákona elektromagnetické indukce. Stačí si v něm jen všimnout znaménka minus.
Externí odkazy
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Autor: Andrejdam, Licence: CC BY-SA 4.0
Experiment showing Lenz's law with two aluminium rings on a scales-like device set up on a pivot so as to freely move in the horizontal plane. One ring is fully enclosed, while the other has an opening, not forming a complete circle. When we place a bar magnet near the fully enclosed ring, the ring is repulsed by it. However, when the system comes to a rest, and we remove the bar magnet, then the ring is attracted by it. In the first case, the induced current created in the ring resists the increase of magnetic flux caused by the proximity of the magnet, while in the latter, taking the magnet out of the ring decreases the magnetic flux, inducing such current whose magnetic field resists the decrease of flux.
This phenomenon is absent when we repeat the experiment with the ring that isn't enclosed by inserting and removing the magnet bar. The induced currents in this ring can't enclose themselves in the ring, and have a very weak field that cannot resist the change of the magnetic flux.
Prepared performed and explained by Prof. Oliver Zajkov at the Physics Institute at the Ss. Cyril and Methodius University of Skopje, Macedonia.
Autor: Andrejdam, Licence: CC BY-SA 4.0
Lenz's law: When electromagnet is switched on, magnetic flux around the ring increases, which causes induction of electric current in the ring. This current creates magnetic field, which opposes to the reason for its existence and that is the rise of the flux. That is the reason why the ring tries to "escape" from that place. When the electromagnet is switched off the process is reversed, but still the ring opposes to the reason for induction of current in itself. Prepared, performed and explained by Prof. Oliver Zajkov at the Physics Institute at the Ss. Cyril and Methodius University of Skopje, Macedonia.