A cylindrical bar magnet is rotated about its axis, as shown in fig. A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then (a) a direct current flows in the ammeter A
(b) an alternating sinusoidal current flows through the ammeter A with a time period T=2Tw
(c) no current flows through the ammeter A
(d) a time varying non-sinusoidal current flows through the ammeter A
