US3663731A

US3663731A - Apparatus for making visible magnetic fields by means of iron filings

Info

Publication number: US3663731A
Application number: US838217A
Authority: US
Inventors: Anders E Ofwerstrom
Original assignee: ANDERS E OFWERSTROM
Current assignee: ANDERS E OFWERSTROM
Priority date: 1968-07-08
Filing date: 1969-07-01
Publication date: 1972-05-16
Anticipated expiration: 1989-05-16
Also published as: SE315155B; DE1933533A1

Abstract

An educational apparatus for displaying magnetic fields has a plurality of cells bordering each other in a flat unit with iron fillings therein and at least a transparent upper limiting surface on said cells. The present invention is concerned with an educational apparatus for making visible magnetic field.

Description

Ilite Stes Uiwerstrom [54] APPARATUS FOR MAKING VISIBLE MAGNETIC FIELDS lBY MEANS OF IRON FILINGS [72] Inventor: Anders E. Ofwerstrom, Kullgardsvagen 21, 44300 Lerum, Sweden [22] Filed: July 1,1969

21 Appl.No.: 838,217

[30] Foreign Application Priority Data July 8, 1968 Sweden ..9360/68 [52] US. Cl. ..35/19A [51] Int. Cl. ..G09b 23/18 [58] Field of Search ..35/l9A,61,66; 46/236, 237,

[56] References Cited UNITED STATES PATENTS 1,549,197 8/1925 l-lanback ..46/237 2,530,013 11/1950 Hanbeck ...46/237 3,426,453 2/1969 Dingwall et a1 ..35/61 Primary Examiner-Robert W. Michell Assistant Examiner-L. Anten AttorneyLinton & Linton [5 7] ABSTRACT An educational apparatus for displaying magnetic fields has a plurality of cells bordering each other in a flat unit with iron fillings therein and at least a transparent upper limiting surface on said cells.

The present invention is concerned with an educational apparatus for making visible magnetic field.

2 Claims, 2 Drawing Figures Patented May 16, 1972 ATTORNEYS APPARATUS F OR MAKING VISIBLE MAGNETIC FIELDS lBY MEANS OF IRON FILINGS The apparatus which has hitherto been used in the educational field of physics for illustrating magnetic fields have been very primitive. In order to prove and detect the appearance of such magnetic fields by means of small iron particles, so called iron filings or swarfs, it has been common practice to spread a predetermined amount of such iron filings upon a plate, whereupon the experiments have been carried out by bringing magnets, coils, solenoids or the like to act upon the iron particles on the plate. It is a time consuming and cumbersome work to uniformly spread the iron filings upon the plate and the teacher has therefore been highly strained. In order to obtain good results it is necessary that the iron particles are uniformly distributed over the effective area of the plate. The more preparation of the plate has thus often required so much time that it has been impossible to fulfill more than one or two experiments during a lesson. After finishing the experiments the teacher has had to gather together the iron filings and it has been impossible for him to prevent getting strongly stained and also the magnets have been soiled by adhering particles, which have been very difficult to remove.

The main object of the present invention is consequently to eliminate the above-mentioned drawbacks and to provide an apparatus, which may be manufactured at low costs and by means of which various experiments may be carried out without any previous preparations. The new apparatus is adapted for use merely by a slight shaking, which means that a considerable number of experiments may be carried out in the same time period, which was earlier necessary for carrying out a single experiments, at the same time as the results will be considerably better owing to the even distribution of the iron filings. To obtain these and other results the apparatus according to the invention is constructed in accordance with the appended claims.

The attached drawing illustrates a preferred embodiment of the invention and FIG. 1 shows a fragmentary section through the new apparatus while FIG. 2 shows a portion of the same in a plan view.

According to the invention the iron filings for making visible the magnetic fields are divided into a plurality of small amounts, which are separated from each other in that each amount is enclosed in a cell structure. The cells illustrate together a magnetic field owing to the fact that the cells are located in close vicinity to each other and that at least the upper limiting surface of each cell is transparent.

Practically this can be achieved in the manner shown in FIG. 1 and 2. From these figures the construction of an apparatus l is apparent, which apparatus includes a base plate 2, preferably made from a transparent material such as transparent acrylic plastic. Upon this base plate 2 is placed a network 3, which preferably is made from textile fibers or from a similar, somewhat resilient material. In the spaces 5, which are generated by the net meshes, iron filings are introduced such that every mesh will contain a certain amount of iron filings, whereupon a upper plate 4, made from transparent material such as acrylic plastic, is applied upon the net work 3. The unit is then sealed by gluing or the like. Instead of a net work 3 it is of course possible to use a plate, provided with a plurality of openings or perforations, which serve the same aim as the meshes. By means of this method an apparatus is obtained, in which iron filings are housed in cells, located in close vicinity to each other, the upper and lower limiting surfaces of which are transparent. By using this apparatus the magnetic fields, generated by magnets and the like, may be easily indicated by means of the iron filings. There is of course no risk for soiling as the iron filings are enclosed in the cells.

The apparatus described and illustrated above is very advantageous in that it is well suited for use in combination with an overhead projector. Owing to the transparency of the apparatus the magnetic fields may be easily illustrated by projection It has been proved that the network, which of course is pro ected at the same time as the magnetic field, has no disturbing effect at all, but it is possible to substantially avoid the visibility of the same by using a transparent material. Magnets, solenoids, galvanometers and the like may be placed upon the unit to make different experiments.

The invention is not limited to the embodiment here shown and described but may be modified within the scope of the appended claims.

What I claim is:

1. Apparatus for making magnetic fields visible for educational purposes, comprising a substantially flat unit having an upper and lower surface, a multitude of discrete cells adjacent each other within said unit, a plurality of iron filings in each of said cells, said iron filings are freely movable only within their respective cells, and at least said units upper limiting surface of said cells being transparent so as to permit viewing of said iron filings.

2. Apparatus as claimed in claim 1, wherein a lattice structure made from a compressible material provides said cells, and both of said upper and lower limiting surfaces covering said lattice structure are transparent to provide said flat unit.