Most of us have seen the device, known as a Van de Graaff generator, that makes your hair stand on end. The device looks like a big aluminum ball mounted on a pedestal, and you can see its effect in the accompanying image.
How does a Van de Graaff generator work?
A Van De Graff Generator is a truly simple high-Voltage generator using a rubber band or belt driven between two pullies which generates possibly thousands of Volts but at very low current. The Voltages generated by these devices can produce truly spectacular displays of a brush discharge. There is one contact (brush) at the bottom to give it a “ground“ and another at the top which collects the charge and conveys it to the smooth metal globe. Any sharp metal point will release a spray called a brush discharge into the air.
How Does a Van De Graaff Generator Work?
If you could shrink yourself until you were really, really tiny, you would find that everything is made out of atoms. Inside each atom are even smaller particles called electrons and protons, which each have an electric charge. Protons are in the nucleus of the atom and are positively charged, while electrons exist in a cloud around the nucleus and are negatively charged.
How A Van De Graaff Generator Works
What I particularly like about the Van de Graaff (or VDG) is that it’s a combination of a few discrete scientific principles and some mechanically produced current, making it an interesting study. For example, did you know that its voltage is limited mostly by the diameter and curvature of the dome? That’s why a handheld one is harmless but you want to avoid getting zapped by one with a 15″ diameter dome. What follows is a journey through the workings of this interesting high voltage generator.
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The Van de Graaff generator is a classroom classic with a surprising heritage in cutting-edge particle physics. As well as making your hair stand on end, these machines were used to accelerate particles through millions of volts.
A person insulated from the ground and touching the dome of the Van de Graaff generator will also lose electrons and become positively charged. The same will happen to each of their hairs. Since the person, their head and each of their hair follicles are all positively charged, the hairs will repel from the head and from every other strand causing them to stick out from the head in all directions.
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The generator makes static electricity the same way you do when you rub your feet on the carpet and then touch a doorknob. Inside the generator is a giant rubber band that rubs across a piece of felt, stealing its electrons. The rubber band then spins around and the electrons travel up to the big metal ball on top. If you have a hand on the metal ball, the electrons will go into you.
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While many of us may not recognise the name, most will undoubtedly have seen its hair-raising effects. The Van de Graaff generator was invented by the American physicist Robert Jemison Van de Graaff in 1931 to create static electricity and make it available for experimentation.