Maximum speed of armature in a motor?

[rowshan]

yeah, when does this occur? In the vertical position or the horizontal? or somewhere in the between?

DC electric motors btw.... =D

[vce08]

When there is the greatest torque.
That is horizontal

[mark_alec]

Not so. Even though the magnitude of the torque is decreasing after the armature is perpendicular to the magnetic field, it will still cause a radial acceleration, increasing the speed of the armature.

There is no easy way to determine where the maximum speed occurs (unless you provide details of exactly what the situation is) for any practical motor, since dissipative forces occur (friction, drag etc.)

[rowshan]

huh? T = F * radius
F doesn't change, neither does radius  to torque remains the same?
I think it is at its greatest just before it comes to the vertical position and it is at its slowest after...
but i suspect we wont be examined on this?

[mark_alec]

huh? T = F * radius
F doesn't change, neither does radius  to torque remains the same?

Not quite. You can model an armature as a dipole in a magnetic field, so the torque will be equal to - so the torque changes with angle.

You would not be expected to know this, or when an armature is moving quickest.

[onlyfknhuman]

huh? T = F * radius
F doesn't change, neither does radius  to torque remains the same?

Not quite. You can model an armature as a dipole in a magnetic field, so the torque will be equal to - so the torque changes with angle.

You would not be expected to know this, or when an armature is moving quickest.

So where not expected on anything about torque?

[mark_alec]

So where not expected on anything about torque?

You are expected to know that torque is at a maximum when the armature is in the same plane as magnetic field, and zero when it is perpendicular, but not need to understand the derivation of it, or what it means with regards to velocity.

edit - fixed up my mistake

[rowshan]

in a motor the armature is always perpendicular to the magnetic field isn't it?

[onlyfknhuman]

So where not expected on anything about torque?

You are expected to know that torque is at a maximum when the armature is in the same plane as magnetic field, and zero when it is perpendicular, but not need to understand the derivation of it, or what it means with regards to velocity.

edit - fixed up my mistake

What sort of question can we possibly get regarding this?