DC motor questions (1 Viewer)

[2671library]

what happens to the coil if you increase the current in a dc motor?

 

[Fizzy_Cyst]

Coil would experience more force, hence torque would increase, hence the coil would rotate more quickly.

 

[2671library]

Thanks. I've got that the force exerted on the coil will increase that can be seen in the equation F=BILsin which will result in an increase in speed of rotation. But aren't torque and speed of rotation inversely proportional?

 

[PhysicsMaths]

Thanks. I've got that the force exerted on the coil will increase that can be seen in the equation F=BILsin which will result in an increase in speed of rotation. But aren't torque and speed of rotation inversely proportional?

What makes you think that?
I think to make the rotational speed increase, more rotational kinetic energy is required, and hence, more rotational force (torque) must be experienced by the coil
So they are probably proportional

 

[InteGrand]

What makes you think that?
I think to make the rotational speed increase, more rotational kinetic energy is required, and hence, more rotational force (torque) must be experienced by the coil
So they are probably proportional

This isn't required for the HSC Physics syllabus, but torque is actually proportional to the rate of change of rotational speed (aka angular velocity).

They are related by the equation , where is the torque, is the moment of inertia, and is the angular velocity (aka speed of rotation).

 

[PhysicsMaths]

Cool.

I was also thinking, consider your statement: torque ∝ 1/speed of rotation
As the speed of rotation approaches 0, i.e. the motor becomes stationary, then the torque experienced by the motor approaches infinity!
Therefore, the rotational force, when rotational speed is really small is almost infinite

Clearly, this cannot be the case, therefore the opposite must be true