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 2.2-cm-diameter wedding band is parallel to the field (E= 4.8 )V.

Part B If the band is made of a gold alloy with resistivity 6.2×108m and has a cross-section area 3.7 mm2 , what is the induced current? Express your answer to two significant figures and include the appropriate units.???

Explanation / Answer

EMF = d(phi)/dt

phi = B*A

EMF = A*dB/dt

EMF = pi*(1.1*10^-2)^2*(2.5 - 0)/(200*10^-6) = 4.75 V

B.

R = rho*L/A

rho = 6.2*10^-8

A = 3.7*10^-6 m^2

L = 2*pi*r = 2*pi*1.1*10^-2 = 0.0691 m

So,

R = 6.2*10^-8*0.0691/(3.7*10^-6) = 1.16*10^-3 ohm

So,

I = EMF/R = 4.75/(1.16*10^-3)

I = 4094.83 Amp.

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