Question

a. A 117‑turn circular coil of radius 2.63 cm and negligible resistance is immersed in a uniform magnetic field that is perpendicular to the plane of the coil. The coil is connected to a 16.7 Ω16.7 Ω resistor to create a closed circuit. During a time interval of 0.125 s,, the magnetic field strength decreases uniformly from 0.447  T to zero. Find the energy, in millijoules, that is dissipated in the resistor during this time interval.

b.

Mindy, a medical device engineer, is designing an apparatus to monitor the breathing of a patient. The apparatus consists of a stretchable loop of conductive material wrapped in a small band around the patient's chest. A constant uniform external magnetic field is produced by a nearby solenoid. As the patient inhales, his chest expands, stretching the chest band. The resulting increase in the area of the loop causes an emf to be induced in the loop. By measuring the induced emf, a device user can estimate the patient's breathing rate.

Mindy needs the apparatus to be able to detect a change in area as small as 4.50 cm² occuring over a time period of 1.50 s. If the minimum emf that can be reliably detected is 2.00×10−4V, what is the magnitude of the minimum external magnetic field that would be needed from the solenoid?

magnitude of minimum external magnetic field:

T

Due to practical constraints, the largest magnetic field that the solenoid can actually produce is 2.40×10−3T. Mindy decides to compensate by using multiple loops of the conductive material in series. How many conductive loops should be in the chest band?

minimum number of conductive loops:

Answer 1