Rebel Compasses—They Point South

Larry Malone, Co-Director of FOSS, Lawrence Hall of Science
March 04, 2002 | Observations by Larry

I recently received this e-mail from a FOSS educator, Melissa Wick, from Fayetteville Public Schools in Arkansas, who came right to the point.

Our school district recently adopted the FOSS kits for our science curriculum. I want to point out a major error in the way the Magnetism and Electricity kit was packaged. Hopefully your manufacturers can correct this error in the future.

In the Magnetism and Electricity kit, drawer 2 contains 48 magnets and 8 compasses, all packed into the same box together. I'm sure you won't be surprised to find out that when our kits arrived, several of the compasses no longer worked. This should definitely be corrected quickly.

Frustrating. I replied, assuring Ms. Wick that Delta Education would make things right and replace the nonfunctional compasses quickly, but went on to suggest another solution to the problem. The compasses were actually working fine—the north seeking pole of the compass needle was pointing north, but it wasn't the painted end of the needle! The needle was reverse-polarized, so it appeared to be pointing south. This is what I suggested to Melissa.

Compass and magnet 1
Compass and magnet 2
Compass and magnet 3

Think about tackling the problem as a project—a learning experience—for teachers and students. Teachers might challenge students to discover a way to "fix" the compasses. This is what I'm thinking.

The compasses are fragile little magnets at best...the needles are small and easily re-magnetized. In the course of using them in classrooms, students inadvertently reverse the polarity—which is what happened to the compasses in your kits by accident in shipment, or even before. The polarity of the compass needle can be easily reoriented as follows.

I will assume you know approximately where north is. Hold up a compass. If the red end of the needle points north, put the compass into the "good guys" pile.

If it points south, bring one of the flat surfaces of a donut magnet (in the kit) up to the compass. One of the points of the needle will quickly point to the magnet—it doesn't matter which one.

Tip the magnet over on top of the compass glass and scoot the magnet quickly across the glass, over the length of the needle, and off on the opposite side.

The needle will now be properly magnetized. The compass can be promoted to the good guys pile. (Repeating the process disorients the needle again, and repeating a third time puts it right again—back and forth; back and forth.)

Now that I ponder it, I'm thinking that the problem may not be in shipping. Simple proximity does not usually alter the polarity—you have to do the "slide-over" business. Magnets and compasses should be able to travel as shipmates without any problems if things are not sliding all over the place. The problem might be in the polarity of the needles at the time Delta Education takes delivery from their supplier. The quest for the final answer continues.