  Assuming the magnetic hypothesis for the formation of warps, we deduce a very
simple formula for the warp curve in an idealized scenario. According to this
formula the warp rises as the third power of radius in the innermost warped
region, reaches the maximum slope at intermediate radii and has an asymptotic
slope coincident with the direction of the extragalactic magnetic field. In
most cases, however, the galaxy's limited size prevents the observation of the
full curve. Even though the model is highly simplified, it basically reproduces
real warp curves, in particular the 21 cm warp curve of NGC 5907. If the
magnetic model were considered to be correct, the fitting of warp curves could
allow rough estimations of the strength and direction of the magnetic field. We
also propose a magnetic field distribution for the outermost part of the
galaxy, matching the boundary conditions of being azimuthal inside, and
constant at infinity. We use this magnetic field distribution to show that the
assumptions made to obtain the warp curve with our simple model cannot
introduce important errors.
