Suppose you are a researcher doing such an experiment in a location where the earth's field is 50 ?T at a 60 ?angle below horizontal. You make a 100cmdiameter, 100-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.
What is the proper orientation of the coil?
What is the necessary current?