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Barlow's Wheel

 

 
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Barlow's Wheel
 
 
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Barlow's Wheel is the name given to an early demonstration of a homopolar motorHomopolar motor

A homopolar motor is of essentially the same construction as a homopolar generator, in general called a homopolar machine....
, designed and built by EnglishEngland

England is the largest and most populous constituent country of the United Kingdom....
 mathematicianMathematics

Mathematics is the discipline that deals with concepts such as quantity, structure, space and change....
 and physicistPhysics

Physics , the most fundamental physical science, is concerned with the underlying principles of the natural world....
, Peter BarlowPeter Barlow

Peter Barlow was an English writer on pure and applied mathematics....
 in 1822. An electric currentElectric current

Electric current is by definition the flow of electric charge....
 passes through the hub of the wheel to a mercuryMercury (element)

Mercury, also called quicksilver, is a chemical element in the periodic table that has the symbol Hg and atomic...
 contact on the rim; this is contained in a small trough through which the rim passes. Due to health and safety considerations brineBrine

Brine is water saturated or nearly saturated with salt....
 is sometimes used today in place of mercury. The interaction of the current with the magnetic fieldMagnetic field

In physics, a magnetic field is that part of the electromagnetic field that exists when there is a changing electric field....
 of a U-magnet causes the wheel to rotate. The presence of serrations on the wheel is unnecessary and the apparatus will work with a round metal disk, usually made of copperCopper

Copper is a chemical element in the periodic table that has the symbol Cu and atomic number 29....
.

"The points of the wheel, R, dip into mercury contained in a groove hollowed in the stand. A more rapid revolution will be obtained if a small electro-magnet be substituted for a steel magnet, as is shown in the cut. The electro-magnet is fixed to the stand, and included in the circuit with the spur-wheel, so that the current flows through them in succession. Hence the direction of the rotation will not be changed by reversing that of the current; since the polarity of the electromagnet will also be reversed."

(Excerpt taken from the 1842 edition of the Manual of Magnetism, page 94)

http://www.physics.montana.edu/demonstrations/video/5_electricityandmagnetism/demos/barlowswheel.html

External links

  • National High Magnetic Field Laboratory