Add Compass


A cross section of three wires carrying unknown currents is shown above.  You can double-click anywhere inside the animation to draw a magnetic field line.  You can also click-drag the wires but this will erase any field line that you have drawn.   You may also add a compass by clicking the “Add Compass” link.


Which wires are carrying current out of the plane of the simulation, that is, out of the computer monitor?           


Instructor Resources

Reference: See Giancoli-PA: 20-5, Giancoli-SE: 27-2.
Answer: Wire 1 and Wire 3. Again, students must use the right hand rule to compare the magnetic field lines on either cross-section of wire to the curl of their fingers and the direction that their thumb points. Here is another interesting example of what can be done depending on how students attack the problem. To determine the direction of the magnetic field, double-clicking gives immediate feedback as shown above for the first and third wires. However, the exact same result can be determined by the careful placing of one or several compasses around a wire as shown around the second wire. With only one compass, getting the same result requires dragging the compass around the wire.
Script Author: Mario Belloni