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-mm-diameter coil of wire circles the subject's cornea while a 1.2 T magnetic field is directed as shown in the figure. The subject begins by looking straight ahead.(Figure 1) Figure 1 of 1The figure shows an eye looking at the top in the uniform horizontal magnetic field B directed to the right. A 6.0-mm-diameter coil circles the cornea of the eye. Cornea 0-6.0-mm-diameter coil O Eye

Part A What emf is induced in the coil if the subject shifts his gaze by 6.0 ∘ in 0.40 s ? Express your answer in volts. Ecoil E c o i l = nothing   V

Answer 1

The area of the coil is, A = ar? =A(3.0x10-² m) = 2.83x10 m2 The initial magnetic flux is, 0 = BA cos 90° = (1.2T)(2.83x10+ m²)cos 90° = 0

The final magnetic flux is, Øs = BA COS(90° – 6.0°) = (1.2T)(2.83x10-4 m²)cos 84° = 3.55x106T The magnitude of induced emf in the coil is, -v(€;-) Δί (3.55x10-6T-0) 0.40s = 1.775x10-4 V