An MRI scanner is based on a solenoid magnet that produces a large magnetic fiel

Question

An MRI scanner is based on a solenoid magnet that produces a large magnetic field. The magnetic field doesn't stop at the solenoid's edge, however, but extends into the area around the magnet. Suppose a technician walks toward the scanner at 0.80 m/s from a region 1.0 m from the scanner where the magnetic field is negligible, into a region next to the scanner where the field is 8.0 T and points horizontally.

As a result of this motion, what is the maximum magnitude of the change in flux through a loop defined by the outside of the technician's head? Assume the loop is vertical and has a circular cross section with a diameter of 19 cm.

What is the magnitude of the average induced emf around the outside of the technician's head during the time she's moving toward the scanner? (The biological effects due to motion in a strong magnetic field include nausea and dizziness.)

Explanation / Answer

speed, v=0.8 m/sec

distance, l=1m

magnetic field, B=8T

diameter, d=19cm

a)

change in flux= B*A

=B*(pi*r^2)

=8*(pi*(9.5*10^-2)^2)

=0.227 Wb

b)

emf=l*V*B

=1*0.8*8

=6.4 v

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