Question

A circular metal ring, as shown on the diagram below, isconstructedso as to expand or contract freely. In a region with aconstantmagnetic field B_o oriented perpendicularto it, the ringexpands, with its radius growing with timeasr=r_o(1+αt²).Asthe ring expands and grows thinner, its resistance per unitlengthchanges accordingtoR=R_o(1+βt²).Findthe current induced in the ring as a function of time. Tocheck youranswer, suppose that B_o =3.00 mT, r_o= 10.0 cm,R_o = 8.00 [ Ω/(m)], α =0.110× 10^-4s^−2,and β = 0.585×10^-2s^−2. What isthe value of theinduced current at t = 74.5 s?(Note: Give the direction ofthe current where when viewed fromabove a positive current willmove counterclockwise.)

http://nplq1.phyast.pitt.edu/res/fsu/capalibrary/65EMInductionFaradayLenz/Graphics/prob05.gif