physics PLZ HELP?

Question

In 1962, measurements of the magnetic field of a large tornado were made at the Geophysical Observatory in Tulsa, Oklahoma. If the magnitude of the tornado's field was B = 13.50 nT pointing north when the tornado was 8.10 km east of the observatory, what current was carried up or down the funnel of the tornado? Model the vortex as a long, straight wire carrying a current.
In 1962, measurements of the magnetic field of a large tornado were made at the Geophysical Observatory in Tulsa, Oklahoma. If the magnitude of the tornado's field was B = 13.50 nT pointing north when the tornado was 8.10 km east of the observatory, what current was carried up or down the funnel of the tornado? Model the vortex as a long, straight wire carrying a current.

plz help

Answer 1

Let's deal with magnitudes first

The B field for a long straight wire is
B=uI/(2πr)

13.5E-9=(4πE-7)I/(2π8.1) ==> I=0.55 A

Now, let's consider direction. Because the direction of the field points north, east of the source, the right-hand rule would have the current flowing from top to bottom.