Physics Question Help (1 Viewer)

[Khan.Paki]

Hey guys,

I got this question I am confused about. When a motor is rotating in a magnetic field:

1) in radial magnetic field = box graph
2) in parallel magnetic field = line curved graph

This is what we were taught in class, as radial magnetic field makes sure torque is constant and maximum at all times, but parallel is only maximum when coil is vertical (greatest cutting of flux).

How come HSC then says the answer is C? Shouldn't it be B?

Thanks

 

[Drsoccerball]

Im pretty sure C is right.

 

[Physicklad]

ooooohhh thats bloody tricky

see the question says force not torque.
this is really important because in F=Bilsin(theta) the theta refers to the angle between the magnetic field and the current. If you look carefully, in this setup, the angle is always 90 regardless of radial or parallel field.
it is, as you said, only torque that is made independent of angle with a radial field