Transcranial magnetic stimulation (TMS) is a noninvasive technique used to stimu

Question

Transcranial magnetic stimulation (TMS) is a noninvasive technique used to stimulate regions of the human brain (see figure). In TMS, a small coil is placed on the scalp and a brief burst of current in the coil produces a rapidly changing magnetic field inside the brain. The induced emf can stimulate neuronal activity.

(a) One such device generates an upward magnetic field within the brain that rises from zero to 1.50 T in 145 ms. Determine the induced emf around a horizontal circle of tissue of radius 1.50 mm. find magnitude and and direction

(b) The field next changes to 0.500 T downward in 90.0 ms. How does the emf induced in this process compare with that in part (a)? find magnitude and direction

Explanation / Answer

E = n delta (BA)/t In this case E is due to a changing field delta B/t = 1.5T/ (145*10^-3)s = 10.35T/s

Assuming coil has 1 turn (n=1)
Coil area A = pi r^2 = pi *(1.8*10^-3)^2 = 10.17*10^-6 m

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