- #1

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Hi!

I have some simple questions on the formula for torque on a coil in a magnetic field, ie this one:

τ = NIA sinθ

where I is the current flowing through the coil, A is the area of one loop, N is the number of loops, B is the magnitude of the magnetic field and θ is the angle between the vector normal to the coil's plane and the magnetic field vector.

All the derivations I have seen to this formula begin with a quadratic single loop, and then in the last step it is said that the derived results apply to coils with N loops of arbitrary geometry.

My questions are: Is the formula still applyable if we have a long solenoid (as in the picture)? Why/ Why not?

If it is applyable: Is it obvious that the torque is around the middle of the solenoid?

If its'nt: Is there any other formula for magnetic torque on a solenoid? Or do you have any suggestion how I could derive one?

Thank you very much! :)

I have some simple questions on the formula for torque on a coil in a magnetic field, ie this one:

τ = NIA sinθ

where I is the current flowing through the coil, A is the area of one loop, N is the number of loops, B is the magnitude of the magnetic field and θ is the angle between the vector normal to the coil's plane and the magnetic field vector.

All the derivations I have seen to this formula begin with a quadratic single loop, and then in the last step it is said that the derived results apply to coils with N loops of arbitrary geometry.

My questions are: Is the formula still applyable if we have a long solenoid (as in the picture)? Why/ Why not?

If it is applyable: Is it obvious that the torque is around the middle of the solenoid?

If its'nt: Is there any other formula for magnetic torque on a solenoid? Or do you have any suggestion how I could derive one?

Thank you very much! :)