electromagnetic concept plz help confused?

Question

I don't understand part c, it asked me to suggest a way to make the coil to rotate continuously.

1.clockwise,anti-clockwise isn't the same as opposite torque?

2.why won't the coil stops at B with the solution's set-up?

photo can't be upload by yahoo knowledge,plz refer to this website:

http://s613.photobucket.com/user/Yan_Wa_Chung/medi...

Answer 1

最愛解答

1. Opposite torques give rise to alternate clockwise and anticlockwise motion.

2. Because the current is being cut off by the non-conducting paint at this orientation, there is no torque acting on the rotating coil. The coil continues to rotate due to inertia.