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[急]點apply lenz's law!???
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考試完全唔明唔明呀!!!!! lenz's law點用?點解架??? 幾時相反??
最佳解答:
Lenz's law (pronounced /?l?nts?z ?l??/) gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. The law provides a physical interpretation of the choice of sign in Faraday's law of induction, indicating that the induced emf and the change in flux have opposite signs. Heinrich Lenz formulated the law in 1834. Definition Lenz's law states that the induced current in a loop is in the direction that creates a magnetic field that is parallel to the change in magnetic flux through the area enclosed by the loop. That is, the induced current tends to keep the original magnetic flux through the field from changing. This law is an example of Le Chatelier's principle of equilibriums, which also involves a system resisting a change in its original state when disturbed. Practical demonstrations A brief video demonstrating Lenz's Law is at EduMation. A neat device made by William J. Beaty levitates a magnet above two spinning rollers. A dramatic demonstration of the effect with an aluminium block in an MRI, falling very slowly. A demonstration that even a child can try: 1- Find a small electric motor. 2- Spin its shaft. 3- Connect its wires together (with a paper clip or alligator clip), and spin the shaft again. 4- This time, the motor resists turning, because current can flow through its wires. Retrieved from "http://en.wikipedia.org/wiki/Lenz%27s_law"
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