Many athletes and cool tech lovers wear a smartwatch, like the Apple Watch, to monitor their fitness and sleep patterns, receive emails, and make phone calls. The watch has an internal battery that is charged wirelessly by induction. The watch is placed faceup onto a charging base (see the photo). There is a charging coil (the primary) in the base and a receiving coil (the secondary) just inside the back faceplate of the watch. An alternating current is sent through the base coil, which creates a changing magnetic field. This produces a change in magnetic flux through the watch's coil, which induces an emf in that coil, thereby charging the watch's battery. Assume the secondary coil has 10 turns with an average area of 1.77 cm. If the emf induced in the coil is 3.80 V, what is the rate of change of the magnetic field within the charging coil? Number i TUE 21 9:33 Calendar Unlock to view (0.0 Receiving coil at back of watch Charging coil In base Units Photo courtesy of David Young