Question

# You are performing studies of the possibility of migrating birds using the Earth's magnetic field for...

You are performing studies of the possibility of migrating birds using the Earth's magnetic field for navigation. To modify the magnetic field in the brain of a bird, you fit the bird with coils as "caps" and "collars" as shown in the figure below.

The illustration shows a bird with a long neck floating in water with metal coils fitted around its head and neck. The "cap" coil rests on top of its head like a crown. An identical second coil, the "collar" coil, encircles its neck just below its head. The planes of each coil are parallel to each other and to the surface of the water. A small button battery is secured on top of the bird's back. A wire running along the back of the bird's head connects the "cap" coil, the "collar" coil, and the battery.

The data on the coils indicate that they each have 210 Ω of resistance, a radius of 1.15 cm, and 50 turns of wire. The centers of the coils are separated by 2.25 cm. You wish to create an "Earth-like" magnetic field of 5.0 ✕ 10−5 T at the midpoint of the axis between the coils. Given this data, you need to determine the voltage of the battery (in V) needed to power the coils.