The Magnet

by Kevin J. Lin

As you may have guessed, not all of the items are necessary for solving the problem. If you had trouble solving it, you were probably thrown off by the red herrings on the table. So which items are necessary?

An obvious (and incorrect) first answer would be the diskette. A floppy disk stores the information in its magnetic media, which is highly sensitive to magnetic fields. However, nowhere in the puzzle is there mention of a computer or other device which could read the disk. It would be impossible to detect the minute changes in the diskette's surface with the items listed. The diskette is a ruse.

The combination of the thread and water may suggest devising a compass of sorts, which would provide a quick solution. But without an iron sliver such as a needle, this is a dead end. If you think you could suspend one bar by the thread to create a "hanging compass," I challenge you to perform this experiment successfully. The thread does not factor into the answer.

The water then? Water actually is full of ions which can be influenced by electromagnetic fields. Perhaps you have seen an experiment in which a stream of water is "bent" by means of a charged wand. Unfortunately, the water is not flowing out of a tap. Worse still, the field generated by an ordinary bar magnet is far too weak to have a visible effect.

The only solution is simplicity in itself. It requires only the two bars. Place the bars so they form a "T" with the blue magnet as the top. A magnet's field is strong at its poles, but nearly non-existent in the middle. If the bars stick, the red bar is a magnet, otherwise it is the blue bar.

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