Question

What is the formula for finding the magnetic field strength outside a solenoid of finite length (also, not on the axis of the solenoid but perpendicular to this axis)?

Answer 1

ampere law

Answer 2

I was under the impression that ampere's law only applied to the inside of the solenoid because of the uniform field.

Answer 3

there is no magnetic field outside of the solonoid

Answer 4

There is a magnetic field outside if the solenoid is finite length...

Answer 5

ah, I see

Answer 6

aka non-ideal

Answer 7

I don't know about non-ideal case

Answer 8

I would think you should just use integration if you know length distance and all just take an element dx at a distance x from the perpendicular find field at Thepoint by biot savart law and integrate.

Answer 9

Even if it were of finite length, the magnetic field would be pretty damn small. Almost negligible. From wikipedia's infinite wisdom: An intuitive argument can also be used to show that the flux density outside the solenoid is actually zero. Magnetic field lines only exist as loops, they cannot diverge from or converge to a point like electric field lines can (see Gauss's law for magnetism). The magnetic field lines follow the longitudinal path of the solenoid inside, so they must go in the opposite direction outside of the solenoid so that the lines can form a loop. However, the volume outside the solenoid is much greater than the volume inside, so the density of magnetic field lines outside is greatly reduced. Now recall that the field outside is constant. In order for the total number of field lines to be conserved, the field outside must go to zero as the solenoid gets longer.