Experiments to study vision often need to track the movements of a subject\'s ey

Question

Experiments to study vision often need to track the movements of a subject's eye. One way of doing so is to have the subject sit in a magnetic field while wearing special contact lenses that have a coil of very fine wire circling the edge. A current is induced in the coil each time the subject rotates his eye. Consider an experiment in which 20 turn, 6.0 a-mm-diameter coil of wire circles the subject's cornea while a 1.4 T magnetic field is directed as shown in the figure. The subject begins by looking straight ahead.(Figure 1)

Express your answer using two significant figures.

Explanation / Answer

Number of turns: n = 20,
Turns per-unit length: N = n/2r = 20/2*3x10-³
magnetic flux density: B = µoNI = 2 T

By Faraday's law of induction:

emf = Bv

angular velocity of shifting eye: = /t = 7°(/180°)/0.2 = 0.61056 rad/s

linear velocity of shifting eye: v = r = (3x10-³)0.610 = 1.83x10--³ m/s

length of centerline path of toroid: = 2r = 2*3x10-³ = 18.8x10-³ m

emf = Bv = 1*(18.8x10-³)*(1.83x10-³) = 34.40x10^-6 volts

Calculations maybe faulty, logic is correct.

Hope this helps :)

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