One safety concern of magnetic resonance imaging (MRI) is what could happen to t
ID: 2304949 • Letter: O
Question
One safety concern of magnetic resonance imaging (MRI) is what could happen to the ions in body fluids if the device's magnetic field were to shut down suddenly due to an equipment failure. An induced emf within the body could cause these ions to flow which would produce an electric current within the patient. Suppose the largest surface of the body through which the magnetic flux passes has area 0.043 square meters and has a normal (perpendicular) aligned with the MRI field of 1.3 Tesla. Determine the smallest time period during which the field can be allowed to vanish if the average induced voltage is to be kept less than 0.010 Volts. Suppose the field were to shut down after only a millisecond due to a power failure. What would be the induced voltage within the patient in this case? 2.Explanation / Answer
induced emf = rate of change of flux
e = A dB/dt = A (delta(B)) / t
0.010 = (0.043)(1.3 - 0) / t
t = 5.6 sec ....Ans
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