Do I have to re-define electric field strength in Centre of Mass frame

[elemis]

So let's say I'm computing the torque as a result of the interaction between two electric dipoles in the lab frame. Let's imagine they are in some electric field.

I then do : τ = r×F

If I now switch to the centre of mass frame I have to find their position vectors from the COM.

Why do I not have to re-define the electric field strength vector and ultimately the force vector on each dipole with respect to the centre of mass frame ?

 

[mfb]

Non-relativistic? Fields and forces (at specific points) are the same in all inertial frames.

 

[elemis]

Non-relativistic? Fields and forces (at specific points) are the same in all inertial frames.

I'll be honest, I don't completely follow what you mean by non-relativistic.

I'm a first year Chemistry student so the idea of inertial frames is a very new concept.

 

[mfb]

I'll be honest, I don't completely follow what you mean by non-relativistic.

Non-relativistic = you don't care about special relativity. Okay, it's fine.

I'm a first year Chemistry student so the idea of inertial frames is a very new concept.

It is just a more general way to say "fields and forces are the same for the lab and the center of mass frame".

 

[elemis]

Non-relativistic = you don't care about special relativity. Okay, it's fine.

It is just a more general way to say "fields and forces are the same for the lab and the center of mass frame".

Oh, okay, I see what you mean now. Thanks !

Beside fields and forces what else does not change between the lab and COM frame ?

 

[mfb]

Masses, relative velocities, distances, all internal paramters of objects, ...
Position, velocity, kinetic energy and momentum (and maybe angular momentum, depending on its definition) are the only changing things, unless I forgot something.