Generator Van de Graaf: the device, the principle of operation and application

The generator of Van de Graaf was invented in the early twentieth century. It was used for various purposes, in particular, for nuclear research. Later the application narrowed. Today you can buy it as a toy and show it to children, levitation of various objects. Also, the generator can be built independently. Then it will become an excellent educational model, with which various experiments are carried out.

Children's tricks

Do you want to create "magic"? Take a bag of polyethylene, cut both ends and tie it on a thread to make a bow. Then the usual ruler of plastic properly rub on the woolen thing and bring it to the bow: the flight will begin ...

A ready "magic wand" with figurines with which you can do such tricks, you can and buy in the store.

But the easiest way to see "magic" is just to pet a cat. Then you can feel and see the static electricity that has arisen.

But the toy, repeating the design of the generator Van de Graaf, runs on a battery. When the button is pressed, an electrostatic charge is created at the tip. Therefore, the figure adopts it, and charges of the same name begin to repel each other. Since the figure is carved in a certain way, it is "inflated" and gets volume. If the charge weakens, you just need to press the "magic" button again.

A bit of history

Of course, the Van de Graaf generator is not just children's toys. The physicist himself created his brainchild for serious research in the section of atomic physics. The first demonstration sample was made in 1929. It was small. More impressive dimensions were received by the Van de Graaf generator installed on rails for airships. The model consisted of two pillars, at the top of which were placed hollow spheres of aluminum with a diameter of fifteen feet.

The installations constructed in 1931 and 1933 reached a power of seven million volts. But only a charge of up to eighty kilovolts was provided by the first generator of Van de Graaf.

Operating principle

Inside, the dielectric tape from paper rotates vertically. The roller located at the top is a dielectric, and the bottom is made of metal and is connected to the ground. The brush electrode in the sphere removes and supplies a charge, which was distributed uniformly in the sphere. Next to the electrode located below, the air is ionized, useful ions settle on the tape, and that part that goes up is charged.

To obtain a high potential difference in linear particle accelerators (for which these generators were needed), two spheres with different charges were used. In one of them, positive ones accumulated, and in the other negative ones. When the concentration reached a certain level, an electric discharge slipped between them. It was he who was investigated. The voltage here reached millions of volts.

Earlier devices were used for nuclear research and particle acceleration. After there were other ways of acceleration, they began to be used in this sphere much less often. At present, the Van de Graaff generator is mostly used for modeling. For example, using it to simulate natural gas discharges. Instead of tapes, installations often use chains consisting of plastic and iron links in turn.

What you need to build the device yourself

The model is easy to build yourself from improvised means. Generator Van de Graaf, assembled with his own hands, consists of the following components:

• Pencil;
• Trimming PVC pipe;
• Rubber bands;
• Paper clips;
• Foil from aluminum;
• The engine from the toy;
• An idle light bulb;
• Dry pastes from the handle;
• Batteries for nine volts;
• Scotch tape;
• Wires;
• Plates.

All elements must be dry, as well as the air in the room. Otherwise, the design will not work or will be, but very weakly.

This is what the generator Van de Graaf will turn out to be. The photo below shows how the model should look.

How the generator is made independently

First, drill a hole on the board, which will become the base of the structure. The drill is selected with a suitable diameter, the shape in the form of a feather. Then on the tube make two holes: top and bottom, for pastes. Make two more holes: one slightly above the top, and the second - perpendicular to the lower one.

Next, the paste must be completely cleaned of ink. Cut a piece corresponding to the inside diameter of the pipe. Take a paper clip, straighten and cut off a piece of sufficient length, so that it protrudes from the tube by a centimeter.

A tape is made of tape. The rubber band is glued so that both sides are also sticky.

Prepared elements are collected.

Add brushes that collect the charge. At the bottom, the brush passes through the hole, and the tip is made fluffy. Brushes should be close to the elastic band, but do not touch it. The upper pass through the hole at the top.

After that, using a foil of aluminum pasted a non-working lamp. The upper wire is attached to the foil. The lamp is inserted on top of the structure.

Van de Graaf's generator is ready.

Experiences

If several threads are attached to the upper electrode and hands are brought closer, they will "stand on end" and wrap their fingers around them. Try to conduct experiments in the dark.

To get a more powerful voltage, connect the two generators.

A good option for the experiments will be the Leyden bank.

The most famous experience is the one in which the hair stands on end. To do this, stand on a rubber mat, wooden board or plywood. The hand is placed on the sphere (the generator must be turned off so that it does not shock). After turning on the device, a spark will pass, causing the hair to stand on end.

The generator should be discharged after each application and work with it very carefully, since the current can become deadly to humans.