Van de Graff Generator

Generally Voltage of Hundreds of thousands of volts can be generated by the Van de Graff generator. Startling releases from the Van de Graff do not represent a serious shock risk as the currents attainable are so small.

There is a pulley which pulls an insulating belt through a sharp pointed metal comb that provides a positive charge by a power supply. Electrons are removed from the belt, leaving it charged positively. The same comb on the top allows for the net positive charge to spread to the dome.

The Van de Graff generator can produce very high potential differences (voltages). In General a small school version can pump a huge charge over the top dome so that the potential difference between dome and the earth is 200,000 volts but the total amount of charge is so small that you only experience a small shock when you touch it. This makes for a possible dramatic demonstration experiment which conveys important ideas about charges and currents.

Working

The rubber belt and band inside the Van de Graff generator runs between two rollers made of different materials, causing electrons to transfer from one roller to the rubber, and from the rubber to another roller, with the triboelectric effect. Top and Down brushes provide the source and sink for these charges, and the upper brush is electrically connected to Van de Graff’s dome so charging will spread throughout the dome.

Now, this accumulative charge would like to spread itself with as much volume as possible, and will also extend to anything you connect to the metal dome, including your volunteer. The reason why it is important to stop them on something electrically- insulating or that the charge would spread out more over the whole world and connecting them to that will greatly reduce the effect, and cause electrical shock as the current flows from Van de Graff to the earth  through its unfortunate human intermediary.

After Insulated, the build-up of charge on the volunteer causes the force light to spread as long as possible, causing the confetti or foil to jump from their hand and cause the hairs on their heads to stand up. When they jump off the chair, the charging quickly flows to the ground and their hair will return to normal immediately.

To work out the voltage of the Van de Graff generator, as well as the voltage on our volunteer, we can use the length of the sparks in combination with the breakdown voltage of air — the electrical voltage needed to break the air into ions and become conductive. . This voltage is about 30,000 V / cm for dry air (hot, humid or low pressure will usually spark easily). Sparks from Van de Graff are usually a few centimetres long, providing a voltage between 50,000 and 150,000 V.

Their tendency to produce sparks is a fundamental limitation of Van de Graff’s Generator, or indeed any accelerated design based on large, unchanging voltage.

Normally, the stored charges on the Van de Graff generator require a way to get into the ground. The earth is very large and the negatively charged particles (electrons) can be very far apart from each other. If a metal ball, attached to the ground when brought near the generator, the charges will jump into the air from the generator to the ball.

Uses of Van de Graff’s Generator

Generally these accelerators are also known as Particle Smashers. The high energy supply by the Generator speeds up the subatomic particles in an evacuation tube, and these particles collide into atoms.

The ability of a Generator to create these powerful high energy collisions is the basis of particles and is used to accelerate the ions, protons, and electrons needed in various Nuclear physics experiments.

Generally these generators are used as accelerators to produce X-Ray poles for nuclear research and nuclear medicine.

Conclusion

The Van de Graff generator is a device that generates a lot of static electricity. Static electricity is made up of extra charges that are stored somewhere so that they cannot move. Usually Charges do not like to be collected in one place.

They like to find opposite charges as partners and avoid particles of the same charge. The Van de Graff generator used can store up to 300,000 Volts of the same kind of charge. Compared to normal house voltage (about 120 Volts) that’s a lot.

The generator makes the electricity static the same way when you rub your feet on the carpet and touch the door button. Inside the generator is a large rubber band that touches a piece of felt, stealing its electrons.