Electric Machines
The first devices for producing electricity were very simple. The ancient Greeks discovered the strange effects of amber rubbed with fur and other material. In the 17th century, scientists used sticks of resin or sealing wax, glass tubes and other objects. By the time of Benjamin Franklin, large glass tubes about three feet long and from an inch to an inch and a half in diameter were popular. These were rubbed either with a dry hand or with brown paper dried at the fire.
There are two major categories of electrical machines: Friction and Influence. A friction machine generates static electricity by direct physical contact; the glass sphere, cylinder or plate is rubbed by a pad as it passes by. Influence machines, on the other hand, have no physical contact. The charge is produced by inductance, usually between two or more glass plates spinning in opposite directions.
All through the 18th and 19th centuries there was tremendous interest in electricity. Scientists such as Franklin, Nollet, Coulomb, Volta, Oersted, Ampère, Ohm, Faraday, Joule and others made major advances. Prior to the invention of the induction coil in 1831 however, the only way to generate high voltage electricity was via static generators such as these.
In devices similar to the Winter Friction Machine shown above, rotating the wheel created a static charge, which was available on the “prime collector” (the brass ball or cylinder at the top or front of the device.) The charge could then be stored in a Leyden jar or measured with an electroscope.
There are two major categories of electrical machines: Friction and Influence. A friction machine generates static electricity by direct physical contact; the glass sphere, cylinder or plate is rubbed by a pad as it passes by. Influence machines, on the other hand, have no physical contact. The charge is produced by inductance, usually between two or more glass plates spinning in opposite directions.
All through the 18th and 19th centuries there was tremendous interest in electricity. Scientists such as Franklin, Nollet, Coulomb, Volta, Oersted, Ampère, Ohm, Faraday, Joule and others made major advances. Prior to the invention of the induction coil in 1831 however, the only way to generate high voltage electricity was via static generators such as these.
In devices similar to the Winter Friction Machine shown above, rotating the wheel created a static charge, which was available on the “prime collector” (the brass ball or cylinder at the top or front of the device.) The charge could then be stored in a Leyden jar or measured with an electroscope.
JOSEPH PRIESTLEY FRICTION MACHINE OF 1769 (REPLICA)
Best known for his discovery of oxygen, Joseph Priestley also experimented with electricity and wrote the first comprehensive history on the subject, published in 1769. The book includes detailed descriptions of several static electricity machines.
Since no complete examples of these machine survive today, Museum curator John Jenkins constructed a faithful reproduction of one machine, using the illustration and description in Priestley’s book as a guide. The wood base was carved to Jenkins’ s specifications by Lee Grindinger, a master furniture maker from Montana. The glass was blown by Seattle artist David Smith of Blowing Sands Glass Studio, and the remainder of the work was done by Jenkins. Shown here, The machine stands about three feet tall, supporting a 10” glass sphere.
Best known for his discovery of oxygen, Joseph Priestley also experimented with electricity and wrote the first comprehensive history on the subject, published in 1769. The book includes detailed descriptions of several static electricity machines.
Since no complete examples of these machine survive today, Museum curator John Jenkins constructed a faithful reproduction of one machine, using the illustration and description in Priestley’s book as a guide. The wood base was carved to Jenkins’ s specifications by Lee Grindinger, a master furniture maker from Montana. The glass was blown by Seattle artist David Smith of Blowing Sands Glass Studio, and the remainder of the work was done by Jenkins. Shown here, The machine stands about three feet tall, supporting a 10” glass sphere.