Faraday's Law Video Lessons

Concept

# Problem: Patients undergoing an MRI occasionally report seeing flashes of light. Some practitioners assume that this results from electric stimulation of the eye by the emf induced by the rapidly changing fields of an MRI solenoid. We can do a quick calculation to see if this is a reasonable assumption. The human eyeball has a diameter of approximately 25 mm. Rapid changes in current in an MRI solenoid can produce rapid changes in field, with ΔB/Δt as large as 50 T/s.Part AWhat emf would this induce in a loop circling the eyeball?Express your answer to two significant figures and include the appropriate units.ε = __________Part BHow does this compare to the 15 mV necessary to trigger an action potential? Choose the best answer.(a) This amount of emf is more than adequate to trigger an action potential.(b) This amount of emf is inadequate to trigger an action potential.

###### FREE Expert Solution

In this question, we are required to use faradays law to determine the emf induced in the human eye.

$\overline{){\mathbf{\epsilon }}{\mathbf{=}}\frac{\mathbf{∆}{\mathbf{\varphi }}_{\mathbf{B}}}{\mathbf{∆}\mathbf{t}}{\mathbf{=}}\frac{\mathbf{∆}\mathbf{B}}{\mathbf{∆}\mathbf{t}}{\mathbf{A}}}$

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###### Problem Details

Patients undergoing an MRI occasionally report seeing flashes of light. Some practitioners assume that this results from electric stimulation of the eye by the emf induced by the rapidly changing fields of an MRI solenoid. We can do a quick calculation to see if this is a reasonable assumption. The human eyeball has a diameter of approximately 25 mm. Rapid changes in current in an MRI solenoid can produce rapid changes in field, with ΔB/Δt as large as 50 T/s.

Part A
What emf would this induce in a loop circling the eyeball?
Express your answer to two significant figures and include the appropriate units.
ε = __________

Part B
How does this compare to the 15 mV necessary to trigger an action potential? Choose the best answer.
(a) This amount of emf is more than adequate to trigger an action potential.
(b) This amount of emf is inadequate to trigger an action potential.