Experiments to study vision often need to track the movement

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 magnetiefield while wearing special contact lenses with a coil of very fine wire circling the edge. A current is induced in the coil each time the subject rotates his eye. Consider the experiment shown in the figure in which a 25-turn, 6.0-mm-diameter coil of wire circles the subject\'s cornea while a 1.3 T magnetiefield is directed as shown. The subject begins by looking What emf is induced in the coil if the subject shifts his gaze by 6 degree in 0.20 s ? Express your answer to two significant figures and include the appropriate units.

Solution

Number of turns: n = 25,
Turns per-unit length: N = n/2r = 25/2*3x10-³


By Faraday\'s law of induction:

emf = Bv

angular velocity of shifting eye: = /t = 6°(/180°)/0.2 = 0.5232 rad/s

linear velocity of shifting eye: v = r = (3x10-³)0.5232 = 1.56x10--³ m/s

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

emf = 1.3*18.8x10-³1.56x10-³ = 38.12x10^-6 volts