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On a torus generated by the rotation of a circle of radius are regularly wound whorls travelled by a current .
On this winding is formed a coil made of whorls of radius .
Compute the coefficient of the mutual inductance of the two windings and .
The flux of the magnetic field created by the torus on the coil is :
Where is the current circulating through the torus.
Ampere's circuital law enables the determination of the field created by the torus inside. It is equal to zero outside.
To simplifiy the computation, the torus is supposed to be thin so that the magnetic field is uniform ( ).
The flux through the coil becomes :