Bats are capable of navigating using the earth's field-a plus for an animal that may fly great distances from its roost at night. If, while sleeping during the day, bats are exposed to a field of a similar magnitude but different direction than the earth's field, they are more likely to lose their way during their next lengthy night flight. Suppose you are a researcher doing such an experiment in a location where the earth's field is 50 at a 60 angle below horizontal. You make a 60 diameter, 250-turn coil around a roosting box; the sleeping bats are at the center of the coil. You wish to pass a current through the coil to produce a field that, when combined with the earth's field, creates a net field with the same strength and dip angle (60 below horizontal) as the earth's field but with a horizontal component that points south rather than north.
#1: what is the proper orientation of the coil?
a. Axis of the coil is horizontal and directed south-north.
b. Axis of the coil is horizontal and directed east-west.
c. Axis of the coil is 60 below horizontal and directed south-north.
d. Axis of the coil is 30 above horizontal and directed south-north.
#2: what is the necessary current?