Magnetic Field for Two Wires in 3-D

Instructions
This simulation shows the magnetic field for a pair of wires. Drag the blue points to adjust the direction and current magnitude of each of two wires. Click a point to toggle between movement in the xy-plane, and along the z-axis. The red vectors represent the current in each wire. Larger magnitudes correspond to larger currents.
  1. Make the current in one of the wires very small so that it can be neglected. What does the magnetic field of a lone wire look like?
  2. Make the currents of the two wires (close to) the same. How does the magnetic field of two parallel wires compare to the field of two anti-parallel wires?
  3. Just by looking at the field, can you tell whether two anti-parallel wires would attract or repel?
– Dave Nero

Information: Magnetic Field for Two Wires in 3-D