A solenoid of length \(40.0 \mathrm{~cm}\) is made of 10000 circular coils. It
carries a steady current of 12.0 A. Near its center is placed a small, flat,
circular metallic coil of 200 circular loops, each with a radius of \(2.00
\mathrm{~mm}\). This small coil is oriented so that it receives half of the
maximum magnetic flux. A switch is opened in the solenoid circuit and its
current drops to zero in \(25.0 \mathrm{~ms}\). (a) What was the initial flux
through the small coil? (b) Determine the average induced emf in the small
coil during the \(25.0 \mathrm{~ms}\). (c) If you look along the long axis of
the solenoid so that the initial 12.0 A current is clockwise, determine the
direction of the induced current in the small inner coil during the time the
current drops to zero. (d) During the \(25.0 \mathrm{~ms}\), what was the
average current in the small coil, assuming it has a resistance of \(0.15
\Omega ?\)