Principle: the magnetic fields of permanent magnets are identical to that of a tightly wound solenoid. Thus, solenoids have "north ends" and "south ends" just as with permanent magnets. Magnetic field lines come out of north ends, and come into south ends. Field directions for solenoids are given by the right-hand-rule: fingers in sense of the current, thumb in the direction of the field.
In the applets below, you can double-click anywhere in the applet window, and a magnetic field line will be drawn at that location. (Try it!) The field line will only have a direction arrow at the point where you click. Also, it may leave the applet window only to re-enter somewhere else. Thus you may want to click in a variety of locations to understand the field directions.
In addition, a small compass is provided. You can drag it to any location. Make sure that the field lines agree everywhere with the orientation of the compass needle.
In each case below, "click up" some magnetic field lines, and answer the associated question.
In the applet above, the gray rectangle could be a permanent magnet, north end on the left. permanent magnet, north end on the right. permanent magnet, north end on top. permanent magnet, north end on bottom. permanent magnet, north end out of page. permanent magnet, north end into page.
In the applet above, the gray rectangle could be a horizontal solenoid, current clockwise as you look down on the right end. horizontal solenoid, current counter-clockwise as you look down on the right end. vertical solenoid, current clockwise as you look down on the top. vertical solenoid, current counter-clockwise as you look down on the top. solenoid, current clockwise in the plane of the page. solenoid, current counter-clockwise in the plane of the page.
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