An airplane flies level to the ground toward the north pole. 

(a) Is the induced emf from wing tip to wing tip when the plane is at the equator greater than, less than, or equal to the wing-tip-to-wing-tip emf when it is at the latitude of New York? 

(b) Choose the best explanation from among the following:

I. The induced emf is the same because the strength of the Earth's magnetic field is the same at the equator and at New York.

II. The induced emf is greater at New York because the vertical component of the Earth's magnetic field is greater there than at the equator.

III. The induced emf is less at New York because at the equator the plane is flying parallel to the magnetic field lines.