Physics Demo Number: 060

Approximate Run Time: 5 min

Magnetic Interactions of a Lodestone in a Dedicated Petri- Dish Boat and Permanent Magnets

Demo Description

Move a lodestone floating in a Petri-dish boat around inside a container of water with the use of a long bar magnet outside the container.

Scientific Principles

  • Magnetic Interactions Between Permanent Magnets

Equipment

  • Lodestone

  • Petri dish

  • Light Pipe water container

  • Long Garland bar Magnets

  • Document Camera

Equipment Location

  • The water vessel resides on [C-1-5] in Kit (053).

  • The lodestone, Petri dish, and Long Garland Bar magnets are in Kit (060) on [B-2-5].

  • The Document Camera is in its storage drawer in the lecture hall.

Instructions

The photo shows a lodestone floating in a dedicated Petri dish (which has plastic yellow tape attached to make rotations easily viewable) in the light pipe water container from demo053.

Bringing a long bar magnet end up near the water vessel at the position of the boat will result in attraction or repulsion of the boat.

It has been found that only 1.75 inches of water in the water container is sufficient to float the Petri dish boat.

Moreover one may then safely set the container on the Document Camera platform in the lecture room and get an excellent display of the floating lodestone boat on the video screen.

(In the past we have tended to fill the container quite full, to get the boat up high enough to be seen directly by the class without much interference by the container wall. This practice of large water content is no longer needed, thanks to the Document Camera, and is indeed potentially more hazardous to the health of the camera.)



Writeup created by David A. Burba
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