During transcranial magnetic stimulation (TMS) treatment, a magnetic ?eld typically of magnitude 0.55 T is produced in the brain using external coils. During the treatment, the current in the coils (and hence the magnetic ?eld in the brain) rises from zero to its peak in about 70 us. Assume that the magnetic ?eld is uniform over a circular area of diameter 2.2 cm inside the brain. What is the magnitude of the average induced emf |£| around this area in the brain during the treatment?

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