A single-turn rectangular conducting coil of area 0.020 m² is mounted on a vertical axle so that the axle passes through the mid-points of two opposite sides of the coil. A uniform magnetic field of magnitude 0.40 T is directed horizontally from left to right. At the instant shown, the plane of the coil is vertical so that its area vector points directly toward the observer.
The coil is suddenly given a brief push so that it begins to rotate about the axle at a constant angular speed. Ignore any electrical resistance except that of the coil’s own wire.
(a) Describe qualitatively how the magnetic flux through the coil changes as the coil turns through the first 90° of rotation.
(b) For the initial clockwise rotation viewed from above, indicate the direction of the induced current in the side of the coil closest to the observer and explain your reasoning.
(c) If instead the coil were pushed so that it began rotating counter-clockwise with the same magnitude of angular speed, how would the direction of the induced current in the same segment compare? Justify your answer.
(d) Suppose the coil were replaced by an identical coil that has four turns tightly wound in the same shape and orientation. Discuss how the magnitude of the induced emf at any instant would compare with that in the single-turn coil, and explain why.