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# Voltage

## The amount of potential energy between two points on a circuit.

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Practice Voltage

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Credit: Greg Peverill-Conti
Source: http://www.flickr.com/photos/gregpc/385191397/

One of the earliest forms of atom smashers, Van De Graaff generators use high voltages of up to 5 megavolts to accelerate electrons to extremely high speeds.

#### Amazing But True

• When a motor is attached to the system and turned on, the lower roller which is covered with silicon turns the attached rubber belt. As the system turns, the lower roller builds a negative charge while the belt builds a positive charge. As the electrons on the roller build up, electrons start to get stripped from the air molecules between the lower roller and the brush. The newly positively charged air molecules get carried on the belt away from the lower roller to the upper roller seen in the image.
• The upper roller is made of a material that tries to repel the excess charge on the belt such as acrylic glass. Any electrons that are in the brush near the upper roller become attracted to the positive charges on the belt. The surrounding air particles break down and their electrons move towards the belt as well. The excess charge that builds up in the system shows up on the outside of the surface of the container.

Credit: Z?tonyi S?ndor
Source: http://commons.wikimedia.org/wiki/File:Van_De_Graaff_gen_04.jpg

Thousands of volts can be generated using a Van de Graaff generator [Figure2]

• Watch the video below to learn how to build a Van de Graaff generator.

#### Explore More

Using the information provided above, answer the following questions.

1. Why must the belt and rollers be made of different material?
2. Why does your hair stand up when you place your hand on a Van De Graaf generator?

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