The iambic trimeter derives its name from its essential shape, which is three metrical units (hence trimeter) which are each basically iambic in form. The iambic metron has the following shape (where the x is an anceps, the - is a longum, and the u is a brevis):
Hence, reversing the current running though a wire will have the affect of reversing the direction of the magnetic force at a point some distance away from the wire. The affect that this has on the overall magnetic field depends on the shape of the wire.
The direction of the magnetic field is counterclockwise or clockwise. For a current flowing in a wire you can use the left hand rule. If you take your left hand and have the thumb point in direction of electron flow in the wire, the fingers wrapped around the wire will show the direction of the magnetic field by the direction the fingers are pointed..