The Van de Graaff generator was invented at the beginning of the twentieth century. It was used for various purposes, in particular, for nuclear research. Later application narrowed. Today you can buy it as a toy and demonstrate to children the levitation of various objects. Also, the generator can be built independently. Then it will become an excellent training model with which they conduct different experiments.
Children's tricks
Want to create “magic”? Take a bag of polyethylene, cut both ends and tie on a string to make a bow. Then rub the usual ruler made of plastic on the woolen thing and bring it to the bow: the flight will begin ...
Ready-made "magic wand" with figures with which you can do such tricks, you can buy in the store.
But the easiest option to see the “magic” is to simply pet the cat. Then you can feel and see the arising static electricity.
But the toy, repeating the design of the Van de Graaff generator, runs on a rechargeable battery. When a button is pressed, an electrostatic charge is created at the tip. Therefore, the figure adopts it, and the charges of the same name begin to repel each other. Since the figure is cut out in a certain way, it “inflates” and receives volume. If the charge weakens, you just need to press the “magic” button again.
A bit of history
Of course, the Van de Graaff generator is not only children's toys. The physicist himself created his brainchild to conduct serious research in the section of atomic physics. The first demo was made in 1929. It was small in size. A more impressive size was received by the Van de Graaff generator mounted 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 built in 1931 and 1933 reached a capacity of seven million volts. But only the first generator of Van de Graaff provided only a charge of up to eighty kilovolts.
Operating principle
A paper dielectric tape rotates vertically inside. The roller located above is a dielectric, and the bottom is made of metal and connected to the ground. A brush electrode in the sphere removes and delivers a charge that is evenly distributed in the sphere. Near the electrode located below, the air is ionized, useful ions settle on the tape, and that part of it, which goes up, is charged.
In order 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 accumulated, and in the other - negative. 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.
Previously, devices were used for nuclear research and particle acceleration. After other acceleration methods appeared, they began to be used in this area much less frequently. Currently, the Van de Graaff generator is more used for modeling. For example, with its help imitate natural discharges of gas. Instead of tapes in installations often use chains consisting of plastic and iron links in turn.
What you need for self-assembly of the device
The model is easy to build independently from the means at hand. Generator Van de Graaff, assembled with his own hands, consists of the following components:
- a pencil;
- PVC pipe trimming;
- gum;
- paper clips;
- aluminum foil;
- engine from a toy;
- broken light bulb;
- dry pastes from the handle;
- nine volt batteries;
- scotch tape;
- wires
- planks.
All elements must be dry, as well as indoor air. Otherwise, the design will simply not work or will, but very weakly.
Here is the Van de Graaff generator. The photo below shows how the model should look.
How the generator is done independently
First, a hole is drilled on the plank, which will become the basis of the structure. The drill is selected a suitable diameter, the shape is in the form of a pen. Then, two holes are made on the tube: above and below, for pastes. Two more holes are made: one slightly higher than the top, and the second perpendicular to the bottom.
Next, the paste must be completely cleaned from ink. Cut a piece corresponding to the inner diameter of the pipe. They take a paper clip, straighten and cut a piece of sufficient length so that it protrudes a centimeter from the tube.
A dielectric tape is made from adhesive tape. Gum is glued so that both sides are also sticky.
Prepared items are collected.
Add brushes that collect charge. At the bottom, the brush passes through the hole, and the tip is made fluffy. The brushes should be close to the elastic, but not touching it. The top is threaded through the hole at the top.
After that, with the help of aluminum foil, an already inactive bulb is pasted over. The top wire is attached to the foil. The lamp is inserted on top of the structure.
Generator van de Graaff training ready.
Experiences
If several threads are attached to the upper electrode and hands are brought closer, they will “stand on end” and put their fingers around. Try experimenting in the dark.
To get a more powerful voltage, two generators are connected.
A good option for experiments would be a Leyden jar.
The most famous experience is one in which the hair becomes on end. To do this, stand on a rubber mat, wooden board or plywood. The hand is placed on a sphere (while the generator must be turned off so as not to be shocked). After turning on the device, a spark will pass, as a result of which the hair will stand on end.
The generator should be discharged after each use and work with it extremely carefully, as the current can become deadly for humans.