Fleming: Left or Right Hand?

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 21 Feb 2010

Fleming, like most people, had two hands. Unlike most, he had a rule for each. But when should you use the left, and when the right?

 LEFT HAND RIGHT HAND A motion occurs due to the current. To work out what direction this motion is in, use the Left Hand Rule. A current is induced in the wire due to the applied motion. To find out in what direction this current flows, use the Right Hand Rule.

Moving a wire in a magnetic field

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 21 Feb 2010
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Brass Pendulum and Lenz’s Law

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 12 Nov 2009

A potential difference is induced across the brass pendulum, and the current flows such that it opposes the motion of the pendulum (due to Lenz’s Law). Brass is not a magnetic material, so the magnet is not slowing down by attracting the brass (as shown by the fact that the pendulum with slits in is not slowed down). However, when the pendulum with slits in is swung through the magnetic field, the eddy currents (which cause the pendulum to slow) are not so free to move within it. Thus Lenz’s Law does not have as much effect; the current does not flow as much, so the motion is not opposed as much. This demonstrates Lenz’s Law, and why a laminated core is more efficient in a transformer.

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