Question

A long, straight, current-carrying wire runs from north to south. If you know the direction of the current, how can you determine the direction of the magnetic field?


a.
Grasp the wire in your right hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.
c.
Grasp the wire in your left hand with the thumb in the direction of the current, the four fingers will curl in the direction of the magnetic field.

b.
Grasp the wire in your left hand with the thumb opposite the direction of the current, the four fingers will curl in the direction of the magnetic field.
d.
Grasp the wire in your right hand with your thumb opposite the direction of the current, the four fingers will curl in the direction of the magnetic field.