This is the boss. No calculator — today $\mu_0 = 1.25\times 10^{-6}\ \mathrm{T\cdot m/A}$, the round number kept for mental work and bench sanity checks, and every value on the page is chosen to fit in your head. One rig, one long problem, and every answer feeds the next: the solenoid's field, then the flux it drives through the search coil, then the EMF as that flux collapses, then the EMF the sliding bar makes in the same field. Write each line down as you go — one early slip rolls all the way to the last.

Watch what the final line actually asks. It does not want another number; it wants a DECISION between two ways of generating, the way a real bench comparison does. The arithmetic is only there to earn you the right to make it.

Everything in the chapter rides in this one bench. 5★ under par here is the chapter crown. Clock in.