How Quickly Can an MRI's Magnetic Field Be Safely Altered?

[kikko]

Homework Statement

One possible concern with MRI (magnetic resonance imaging) is turning the magnetic field on or off too quickly. Bodily fluids are conductors, and a changing magnetic field could cause electric currents to flow through the patient. Suppose a typical patient has a maximum cross-section area of 6.8×10−2 m^2.

What is the smallest time interval in which a 5.5 T magnetic field can be turned on or off if the induced emf around the patient's body must be kept to less than 9.0×10−2 V?

Homework Equations

No idea

The Attempt at a Solution

Last problem on my assignment, I have no idea where to even start with this one.

 

[MCG93]

Magnetic flux (Phi) = Magentic flux density (B) x area of cross section (A)

Induced emf = rate of change of magnetic flux, i.e. Phi/time

so, in other words, since you have the Magnetic flux density (5.5 T), the area of cross section (6.8×10−2 m^2), and the emf that is limited to 9.0×10−2 V, you can easily find the smallest time interval, as any smaller would give an emf larger than the specified.

Hope that was of help, if it has not been too late to answer this question.