7a)

• The induced emf is directly proportional to the rate of change of flux linkage (for a coil) ,
• or rate of cutting of flux (for a moving wire) .
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• 7b)

Think of the tube as consisting of many circular rings.

As the magnetised steel block moves through each ring, the ring experiences a changing magnetic flux linkage. Hence e.m.f is induced around the ring.

Since copper is a conductor, an induced current follows.

The induced current results in a magnetic force on the steel block. By Lenz’s law, the magnetic force must always act upward to retard the motion of the steel block, which is the cause of induction.

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