Green turtles are thought to navigate by using the dip angle of the earth’s magnetic field. To test this hypothesis, green turtle hatchlings were placed in a 72-cm-diameter tank with a 60-turn coil of wire wrapped around the outside. A current in the coil created a magnetic field at the center of the tank that exactly canceled the vertical component of the earth’s 50 μT field. At the location of the test, the earth’s field was directed 60° below the horizontal. What was the current in the coil?

Green turtles are thought to navigate by using the dip angle of the earth’s magnetic field. To test this hypothesis, green turtle hatchlings were placed in a 72-cm-diameter tank with a 60-turn coil of wire wrapped around the outside. A current in the coil created a magnetic field at the center of the tank that exactly canceled the vertical component of the earth’s 50 μT field. At the location of the test, the earth’s field was directed 60° below the horizontal. What was the current in the coil?