Objective:
-To show that the magnets (arrows) in a compass align with the direction of external magnetic fields, thus making compasses unreliable in presence of other magnets.
Apparatus:
- 20 mini compasses
Method:
Arrange the compasses in a circular pattern plate (see image below).
The north arrows of the compasses will no longer be pointing north, but towards the south arrow of the adjacent compass. Any single compass can now be taken out of the circle to show it is indeed a working compass that points north when not part of the circle.
Notes:
- Because the circle of compasses takes some time to troubleshoot if one of the compasses is incorrectly magnetized, it shall be the responsibility of the technician to pre-arrange the circle of compasses and to ensure the compasses are correctly magnetized prior to the start of the lab (correctly point north in the absence of an external magnetic field and follow the circular pattern when put in a circle).
- If one of the compasses is magnetized in the opposite direction, it can be corrected by brining a cow magnet to the edge of the compass, and passing it very rapidly across the compass face along the direction of the needle.
