Magnetic field created by long wires with electric current

Program to visualize the magnetic field produced by long, current-carrying wires.
You can choose to show two or three wires.
Click on a wire to start moving it with the mouse.
Click again to fix its position.
Shows magnetic field direction as green arrows.
Shows magnetic field lines in yellow.
You can change the magnitude of any current, select it and use the slider to do so.