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Lenz’s Law

Lenz’s Law. There is a minus sign in Faraday’s Law. Relates flux change to polarity of emf Lenz’s Law restates this connection. Minus Sign. The induced emf will produce a current that acts to oppose the change in magnetic field. As the magnetic flux increases the current increases.

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Lenz’s Law

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  1. Lenz’s Law

  2. There is a minus sign in Faraday’s Law. Relates flux change to polarity of emf Lenz’s Law restates this connection. Minus Sign The induced emf will produce a current that acts to oppose the change in magnetic field.

  3. As the magnetic flux increases the current increases. The current creates a magnetic field in an opposite direction to the increasing external field. As the field decreases the induced current creates a field that replaces the lost field. Opposing Change

  4. A looped coil has 200 turns, resistance of 5 W and an area of 0.25 m2. It is in a 0.40 T downward field and is squashed to zero area in 100 ms. What happens to the current? The flux is reduced by the shrunk area. DF = -.100 T m2 The current will flow to create a replacing magnetic field. The current will flow counterclockwise seen from above. Squashed Coil

  5. Magnetic levitation uses opposing magnetic fields. Current in the track sets up a field to oppose moving magnets in the train. The force can lift the entire train off the ground. Maglev

  6. A solid metal plate is affected by Lenz’s Law. A current can move through the metal. Eddy currents will circulate to oppose the change in field. The motion can also slow to resist the change. Eddy Currents next

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