Contact
Back Next Home

Magnetism and Electromagnetism

 

Development of the Electromagnet

In 1819, Hans Oersted (1777-1851) found that an electrical current, when passed through a straight piece of wire, deflected the needle on a compass. He published his findings in a small pamphlet in 1820, probably one of the last great scientific discoveries to be published entirely in Latin. 


Sturgeon's Electromagnets

His discovery showed there was a connection between electricity and magnetism and prompted a whirlwind of further investigation by others.  In 1825 William Sturgeon developed the first practical electromagnet by loosely winding a coil of un-insulated wire around a horseshoe-shaped piece of iron. To prevent the wire from shorting Sturgeon coated the iron in varnish. The seven-ounce magnet was able to support nine pounds of iron using the current from a single cell.

In 1830, Joseph Henry dramatically improved on Sturgeon's electromagnet by using cotton insulated wire (probably the first time this was done) and winding hundreds of turns around an iron core.  With other modifications, Henry constructed  21-pound "experimental magnet" able to support 750 pounds.

Magnetic/Electromagnetic Apparatus from the collection:

 


Apparatus to Demonstrate Oersted's Discovery
likely by Watkins and Hill
1830-1845

 

Collection of Electromagnets
1830 - 1845

Including red and green painted coil by Daniel Davis (12 o'clock in illustration) circa 1840's; Watkins and Hill electromagnet (3 o'clock, circa 1840's); English horseshoe electromagnet(6 o'clock) circa 1870's; Primitive electromagnet, American circa 1830's (9 o'clock) circa 1830-1845

 

  

Electromagnet with Three Poles
Daniel Davis or Benjamin Pike
1848

.

Helix on Stand
Daniel Davis or Benjamin Pike
1848

 

  

Helix on Stand
Daniel Davis
1840's

Ampère Table

Named for André-Marie Ampère, (1775 - 1836) This is an early model of the same apparatus constructed by Ampere for his famous experiments on the relationship between magnetic fields and electric current.		  
 

Early Electromagnet Demonstration Apparatus - 1852

This early demonstration model was made to show the force of the electromagnet. A label under the bottom reads : " ALLEGORY OF THE NEW FORCE WHICH SUPPORT THE WORLD." The allegory is represented by the heavy iron globe which can be attracted by the magnet . The globe is made from an old armillary sphere and is dated 1852.  The apparatus is signed " Arnaldo Volpi costruttore -Torino " ( Italy)

 

Ten Small Toy magnetic Tops
1920's

  
Permanent Magnet Demonstration Apparatus
1860

This device is similar to the electromagnet demonstration below, except that a horseshoe permanent magnet is used. 


Magnet Toy - 1824 or 1842


Magnetic Toy - George Adams
From the King George III Collection
Reproduced from "Public & Private Science"
by Morton & Wess, London

The mahogany box measures 10-3/4" x 2-3/4" and contains four squares of ebony with ivory inserts with the numbers "1842" on the surface of the ivory. Each square contains a concealed magnet. Unsigned but very similar to item number E71 described and illustrated on pg 445. of Public and Private Science, The King George III Collection, Morton and Weiss, London 1993.

The toy is missing it's "key", shown in the upper portion of the illustration on the right.  The key contains four paper disks which are mounted like compass needles and are free to rotate.  To operate the puzzle, the host invites a guest to rearrange the ebony chips in any order and close the case, while the host's eyes are averted.  The host then places the "key" on top of the still closed puzzle and reads the correct answer from the key, amazing his guests.   What the guest can't see is a small iron bar attached to each disk inside the key that causes the disk to align with the numbered ebony chip in the puzzle.  The magnetic attraction causes the iron bar to align with the chip, bringing the appropriate number to view in the window.

Barlow's Globe  c.  1895


A Wonderful and very rare giant magnetic GLOBE, signed "Hopfer & Reinhardt - Mechanicker & Opticker -Innsbruck ( Austria late 1800/early 1900's . In 1600 William Gilbert constructed a globe of lodestone (magnetic ore) to demonstrate the phenomena of the earth's magnetic field. After the discovery of the electromagnetism, physicists such as Barlow and Nobili made electric globes like this one to visualize the earth magnetic field. This globe is constructed of  two hemispheres made of very heavy cast brass which conceal an electromagnet inside. The poles of the electromagnet correspond to the poles of the globe. A needle supported by an ornate brass base indicates the magnetism produced by the globe.

 

Nobili Sparking Magnet  - 2nd Qtr, 19th Century


Nobili Sparker
(Italian)
2nd qtr, 19th Century

Leopoldo Nobili (1784 - 1855) was professor of physics at the Royal Museum.  He is best known for the invention of a number of instruments that he used to demonstrate various principles of physics. 

Around 1832 Nobili and the director of the museum were  inspired to develop the sparking magnet after reading a description of an experiment by Michael Faraday where he was able to obtain a spark from an electromagnet.  

This device is operated by rapidly swinging the magnet through the magnetic field produced by the horseshoe magnet.  The resulting induced current in the coil produces a spark when the ends of the coil come into contact with the magnet. These devices where used in demonstrations sometimes to ignite a Volta Hydrogen Lamp.

 

Tuning Fork Audio Oscillator
Max Kohl
(German)
1900

  

Groves Earth Coil
(English)
1900

A coil of wire mounted to a commutator rotated so as to cut the lines of force of the earth's magnetic field, thereby generating a potential difference. This  apparatus was used to demonstrate the earth's magnetic field.

 

GROUP OF COMPASSES
English
Last Quarter, 18th Century.

From left to right: (1) Pocket compass - mahogany box measures 2" x 2" with primitive triangular shaped hinges; in very fine condition: See pg 443. Public and Private Science; The King George III Collection, fig. E68; (2) Pocket Compass - signed "Benjn Pike, Optician and Philosophical Instrument Maker, 12 Wall St. New York" Same as above except measures 2-5/8 " square and is painted/waxed red on top of box enclosure. Benjamin Pike Sr., was at this business address from 1804 to 1831; it is very rare to find instruments signed by Benjamin Pike, Sr. (3) Pocket Compass - same as above except measures 4" x 4" and has square hinges.

    
 
Contact

Back Next Home