Bats can navigate using the earth’s field—a plus for an animalthat may fly great distances from its roost at night. If, whilesleeping during the day, bats are exposed to a field of a similarmagnitude but different direction than the earth’s field, they aremore likely to lose their way during their next lengthy nightflight. Suppose you are a researcher doing such an experiment in alocation where the earth’s field is 52 µT at a 60° angle belowhorizontal. You make a 50-cm-diameter, 100-turn coil around aroosting box; the sleeping bats are at the center of the coil.
a) Draw a diagram of the field and compute the magnitude of thehorizontal and vertical components. The horizontal component pointsnorth.
b) If you add a horizontal field that is double the earth’shorizontal field but that points south, what is the new horizontalcomponent?
c) Describe the magnitude and direction of the total field. Howmight you expect this to affect the bat’s navigation?
d) What current do you need in the coil to produce the notedfield? What is the necessary orientation of the axis of thecoil?
