An astronaut is connected to her spacecraft by a 25.0-m-long tether cord as she and the spacecraft orbit the Earth in a circular path at a speed of 7.80 × 10 3 m/s. At one instant, them between the ends of a wire embedded in the cord is measured to be 1.17 V. Assume the long dimension of the cord is perpendicular to the Earth’s magnetic field at that instant. Assume also the tether’s center of mass moves with a velocity perpendicular to the Earth’s magnetic field. 

(a)Determine the magnitude of the Earth’s field at this location? 

(b) Does the emf change as the system moves from one location to another? Explain. 

(c) Provide two conditions under which the emf would be zero even though the magnetic field is not zero.