1. The problem statement, all variables and given/known data http://i.imgur.com/EHokd.png Two long wires carry currents I1 and I2 as shown in the figure. The first wire runs parallel to the x axis but is a distance d above the x-y plane. The second wire lies along the y axis and passes through the origin. What is the direction of the torque on the wire carrying I1 due to the current I2 in the other wire? (a) in the positive y direction (b) in the positive z direction Correct Answer (c) in the negative y direction 2. Relevant equations F=BI X L 3. The attempt at a solution I first use Ampere's law to find magnetic field caused by I2 which is counterclockwise. However, then how should I use RHR to determine force direction? How about torque direction? Is torque direction just used RHR for force and distance torqure= Fd? Is there any difference if instead I use RHR from I to B or B to I? Thanks!