Chapter 20, Problem 12P

Medical devices implanted inside the body are often powered using transcutaneous energy transfer (TET), a type of wireless charging using a pair of closely spaced coils. An emf is generated around a coil inside the body by varying the current through a nearby coil outside the body, producing a changing magnetic flux. Calculate the average induced emf if each 10-turn coil has a radius of 1.50 cm and the current in the external coil varies from its maximum value of 10.0 A to zero in 6.25 × 10⁻⁶ s. (Hint: Recall from Topic 19 that the magnetic field at the center of the current-carrying external coil is $B=N\frac{{\mu }_{0}I}{2R}$. Assume this magnetic field is constant and oriented perpendicular to the internal coil.)