56. Calculate the current carried in a 175-turn circular loop 18.0 cm in diameter to create a maximum torque of 27 Nm if the strength of the magnetic field in which the loop rotates is 1000 times that of the Earth. (Recall that Earth's magnetic field has an average strength of 10-4 T.) 57. Barbara is hiking and carrying a navigational compass, and she walks beneath an overhead transmission line approximately 6.00 m above the compass. The current in this transmission line is 1.00 kA. Determine the strength of the magnetic field at Barbara's compass.