Faraday's law of induction: question?

Question

An MRI tech. moves his hand from a region of very low magnetic field strength into an MRI scanner's 2.00 T field with his fingers pointing in the direction of the field. What is the average emf induced in his wedding ring? given its diameter is 2.20 cm and assuming it takes 0.250 s to move it into the field.

Answer 1

The area of the ring is:

A = πr² = π x (0.011 m)² = 3.80 x 10^-4 m²

The change in magnetic flux is:

∆Φ = BA = 2.00 T x (3.80 x 10^-4 m²) = 7.60 x 10^-4 Wb

The induced emf is:

|Ɛ| = ∆Φ / ∆t = (7.60 x 10^-4 Wb) / 0.250 s = 3.04 mV