Letter from Alessandro Volta to the Royal Society of London, March 1800. "The apparatus of which I write, and which will doubtless astonish you, is nothing more than a collection of good conductors of different sorts arranged in a certain way, 30, 40, 60 or more pieces of copper (or better, silver), each one resting on pieces of tin or better of zinc, and an equal number of layers of water or some other fluid that is a better conductor than pure water, such as salt water, lye, etc., or pieces of cardboard or leather soaked in these liquids. This is everything that constitutes my instrument."

In this way, and by means of a chemical reaction between zinc and the liquid, electricity is generated.

How to use: loosen the nut on the top. Dismount the discs and soak the felt with salt water. Assemble in the following order: fixed zinc disk, cloth, copper disc, zinc disc, cloth, and repeat until the end. In this way a voltage of 4.5v is produced.

Hand-made piece. Materials: copper, zinc, brass and boxwood. Dimensions: h=42cm. Design: Alessandro Volta, 1850.

Ramsden's electrostatic machine is the result of the improvements that he made in 1766 to the primitive electrical machine of Otto Von Guernicke. This consisted of a sulfur sphere that was turned by hand, while the other rubbed against the sphere. Ramsden replaced the sulfur sphere by a glass disc, and the rubber by four pads.

The theory of the electrical machine is extremely simple: while the disc is rotating, it yields its electrons to the pads by rubbing against them so they become negatively charged. This charge, however, is lost to earth because it passes through the strips of tin and the chain. The glass, which has been left with a positive charge, exerts an influence on the combs of the machine and attracts the electrons by the points that recover the neutral state. With this the ball, which is also metallic, is charged positively and if a hand is put close to it a spark will jump and continue to do so while the disc is being turned.

For the best operation of the machine it is important that it is completely dry and safe from humidity. The yield of the machine also improves if the glass disc is dusted with sulfur.

Hand-made piece. Materials: copper, brass, glass, tin, bubinga wood and American walnut, silk and leather. Dimensions: h = 28cm. Design: Jesse Ramsden, 1766.

James Wimshurst (1832-1903), an English engineer, developed an electrostatic machine used to produce electrical charge. It consists of two crystal discs with metallic pieces placed near the edges. When driving the crank, the two wheels to turn in opposite directions, when the sectors graze each they load themselves, storing the load in bottles of Leyden. When the load is great, a spark occurs between two spheres (unloading spheres). It even works well in humid atmosphere. Wimshurst' machines with discs of up to 2 meters of diameter have been constructed.
In addition to its use in laboratory demonstrations, it was used for medical treatments, abtaining a high voltage for the first x-rays tubes.

 

Hand-made piece. Materials: aluminum, receives, glass, tin, wood of bubinga and American walnut. Dimensions: h = 40 Design: James Wimshurst, 1880

The droplet of Kelvin is a simple electrostatic generator and at the same time original that separates the positive electrical charges and existing refusals in the water by the share of the gravitational field. This in another way, transforms directly the gravitational potential in a potential difference electrical.

The drops fall from a deposit and form two rows that go across some rings of copper finally to fall in two containers, where opposed electrical charges with typical potential differences of 10 or 15 kilovolts are stored. The crossing of the fluid through the metallic rings is the one responsible for the appearance of the voltage among the inferior containers. After few minutes, it|he|she will jump between both drivers a spark that can arrive at the 10 linear millimeters.

Part prepared by hand. Materials: copper, brass, water pump, methacrylate and wood. Dimensions: h= 45 cm. Design: Marc Boada, 2006

The electroscope is an instrument that shows the presence of an electrical charge. It was made for the first time in 1705 by Haukesbee and consisted of two straws suspended face to face at the lower end of a metallic rod. The straws were later replaced by light, gold leaves.

Its operation is very simple: when an electrified body (like, for example, a rod of sealing wax rubbed against cat's fur or a piece of wool) is brought slowly towards the upper ball of the apparatus, the gold leaves are charged with the same type of electricity and they repel each other.

We could describe this instrument as the predecessor to the present tester.

 

Hand-made piece. Materials: gold leaf, glass, brass, walnut wood. Dimensions: h=18cm

The lightning rod, invented by Benjamin Franklin (1706-1790), is a metal point on a building connected by a conductor to the ground, thus assuring that if lightning strikes the building the current passes through the metal instead of the building.

 

 

 

 

Hand-made piece. Materials: copper, brass, wood. Dimensions: 32,5cm

When a magnetized needle is suspended of a thread, it is observed that the needle, instead of stopping in any position, always finishes because it|she notices a specific address, determined through the terrestrial magnetic field. Several analogous observations having been carried out in all the points of the balloon, our planet to an immense magnet whose poles would be near the terrestrial ones has been compared.

This directive action|share of the Earth on the magnets is the base on which the compasses, instruments of direction used basically in navigation and topography, that indicate horizontal addresses from the approximate address|direction North-South are built.

The origin of the compass is not known for sure, although its invention to the Chinese is attributed around the XI century. Before its use in navigation, the marines did not have more guide that the Sun or the Polar star in its directions, for what always sailed near the coasts.

Part prepared by hand Materials: glass, brass, wood of American oak, magnets of neodymium and needle of steel Dimensions: 15 cm of diameter

The magnetite (Fe304) is a mineral with interesting magnetic properties. For centuries it was the only well-known magnet. Its weak natural magnetism was reinforced by means of pure iron plates that channel the lines of magnetic field, thus obtaining remarkable forces that allow to support weights 20 times itself. Today we can see magnetites of tens of kilos, supporting huge weights for hundreds of years. Good examples of this piece are in the Museum of Natural Sciences of Madrid and in the History of the Science of Florence.

 

 

 

Hand-made piece. Materials: wood, brass, iron and magnetite. Dimensions: 45 cm in lenght

This levitator consists of two neodymium magnets, one stronger than the other, and two "magnetic brakes" which are made of copper. The neodymium magnets create an electrical current between themselves and "levitate." An experimenter who takes the magnet between their fingers will notice a strong drag. This follows the rule of Lenz, which states that the direction of an induced electric current is always such that the magnetic field they produced opposes the magnetic field inducing it.

 

 

 

Part prepared by hand Materials: charge, ceramic magnets of neodymium, methacrylate, and wood of bobinga.