A TMS (transcranial magnetic stimulation) device creates very rapidly changing m

Question

A TMS (transcranial magnetic stimulation) device creates very rapidly changing magnetic fields. The field near a typical pulsed-field machine rises from 0 T to 2.5 T in 200 s. Suppose a technician holds his hand near the device so that the axis of his 2.1-cm-diameter wedding band is parallel to the field. Part A: What emf is induced in the ring as the field changes? Express your answer to two significant figure E= ________ unit____ Part B: If the band is made of a gold alloy with resistivity 6.2×108m and has a cross-section area 4.5 mm2 , what is the induced current? Express your answer to two significant figures and include the appropriate units. I= _______ units____

Explanation / Answer

(A) induced emf = rate of change of magnetic flux

= d (B A )/dt

= A dB/dt

= (pi (2.1 x 10^-2 / 2)^2) (2.5)/(200 x 10^-6)

= 4.33 Volt ....Ans

(B) R = rho L / A = (6.2 x 10^-8) (pi x 0.021) / (4.5 x 10^-6)

R = 9.10 x 10^-4 Ohm

I = V/ R = 4764 A

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