Moment of inertia of a charged spinning top

[JCOM44]

How can I calculate the moment of inertia of a spinning top with charge Q submerged in an electromagnetic field?

I've already calculated it for the case with no charge, but I don't know how to do this.

 

[FactChecker]

I'm not aware of any context where charge has anything to do with the moment of inertia.

 

[JCOM44]

But the electric field generates a dipolar moment, which makes the spinning top rotate different affecting the moment of inertia, isn't that right?

 

[FactChecker]

That sounds to me like an object with a particular moment of inertia, based only on the location of it's mass, reacting to a force from the electric field. The moment of inertia is not a function of the force field.

 

[Vanadium 50]

isn't that right

No.

The moment of inertia is the same. The forces and torques on the top could be different, but the moment of inertia is the same.

 

[JCOM44]

Can't I consider the dipolar moment as an electromagnetic analogue of the moment of inertia?

 

[Vanadium 50]

I don't know what good that will do.

 

[JCOM44]

Then would you say that when we have a charged spinning top with a defined moment of inertia and it is suddenly exposed to an electromagnetic field, the way it rotates won't change?

 

[Vanadium 50]

If the field applies a force or torque to the top, it's motion will change. But it's moment of inertia will not.

 

[Fervent Freyja]

Maybe it will help if I put it this way: would anything change if you put a (charged) ballerina in an electromagnetic field to execute her fouettes?



Ballerina's would make excellent physicists.

 

[A Lazy Shisno]

An object's moment of inertia is merely the extent to which it resists rotational acceleration about a particular axis. It's a product of the object's mass and dimensions, it actually has nothing to do with motion.

Take the moment of inertia of a solid sphere for example, which can be expressed as
$$I=\frac{2}{5}mr^2$$
As you can see, motion doesn't play a part whatsoever (we're talking classically here).

 

[CWatters]

Even a force like friction doesn't change the moment of inertia.

Perhaps the OP is confusing momentum and moment of inertia?