Explanation of how to generate static electricity - Succeed in Physical Science. Also refer to physics, electricity, Van de Graaff, Wimshurst, AC, DC, magnetism, lightning, Leyden jar, education, Ron Kurtus, School for Champions. Copyright © Restrictions
Generating Static Electricity
by Ron Kurtus (revised 24 June 2006)
There are two good static electricity generators that are used in many schools and laboratories. One of them is the older Wimshurst Electrostatic Generator and the other is the newer Van de Graaff Generator. Both are capable of generating high power static electricity, sufficient to shoot sparks, cause the hair on your head to rise and light fluorescent bulbs.
Questions your may have include:
- How does the Wimshurst Electrostatic Generator work?
- How does the Van de Graaff Generator work?
- What can you do with those devices?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Useful tools: Metric-English Conversion | Scientific Calculator.
Wimshurst generator
The Wimshurst electrostatic generator was invented in the 1880s. The modern version consists of two plastic discs that are rotated in opposite directions by a hand-crank and drive belt mechanism.
Wimshurst Electrostatic Generator
How it works
The way it works is that a number of metal foil sectors are cemented onto two discs. As the discs turn, each metal foil sector accumulates the charges through contact with brushes on bars near the front and back of the discs. Two additional pairs of brushes collect the accumulated charges and transmit them to the storage capacitor, such as a Leyden jar
The brushes also are connected to spark gap electrodes. As the discs revolve, a high voltage spark can jump between the electrodes if they are gradually brought together.
Generates 75,000V
The Wimshurst electrostatic generator can generate up to 75,000 volts. Since the current is very low, there is little danger from the high voltage, but yet it is effective for creating sparks and performing interesting static electricity experiments.
Van de Graaff generator
The Van de Graaff generator can develop potential energy of as high as 400,000 volts, and it will develop sparks up to 15 inches (38 centimeters) in length.
Relatively safe
It is relatively safe to use though, since the current is only 10 microamps (10/1,000,000 amps). This is because electrical power equals the voltage times the amperage. 400,000 volts times 10 microamps equal only 4 watts—the energy to light a flashlight bulb.
Person touching a Van de Graaff Generator
How it works
The Van de Graaff generator is powered by a high speed electric motor. It has a belt running on two pulleys. The lower pulley is made of an insulating material and the upper pulley is made of metal. There is a grounded comb close to the belt in front of the lower pulley, and another inside the terminal, close to the belt in front of the upper pulley, connected to the terminal.
Adhesion between the belt and the lower pulley charges the pulley, and it attracts opposite charges to the outer surface of the belt from the grounded comb. The belt then transports these charges to the terminal, where they are collected by the upper comb and transferred to the terminal. The shielding provided by the terminal allows the continuation of the process even if the terminal is already strongly charged. The high speed of the belt, along with the large discharge electrode, allows the continuous buildup of charges and great voltages to be achieved.
Various sizes
The Van de Graaff generator in the picture is about 35 inches (90 cm) high. Some scientific laboratories have such generators several stories high. They can develop sparks that go all the way across the room. But still that doesn't compare to the power of lightning, which can be several miles long.
Demonstrating static power
Besides being able to create fairly large sparks, these static electricity generators can be used for other experiments.
Large Van de Graaff
The simulation below shows how two large Van de Graaff generators can send large sparks across the gap.
Simulation designed by Jim Bumgardner
You can adjust the knobs with your mouse to change the look of the lightning sparks.
- Detail concerns how jagged the spark is.
- Thickness is the thickness of the spark.
- Number bolts is the number of lightning bolts.
- Displacement concerns how much the sparks vary from the direct path.
These items are somewhat related to real world parameters but are more for demonstration than scientific simulation.
Other experiments
When a person puts his or her hand on the globe of the Van de Graaff generator, the person's hair will stand on end. This is because the static charges collect on the hair and like charge repel, thus repelling the hairs from each other.
When you take a fluorescent bulb and bring it near a Van de Graaff generator, the charges excite the atoms inside the bulb, cause it to glow--even if the bulb is not plugged in.
Summary
The Wimshurst and Van de Graaff generators are two good sources for generating static electricity. Both use high-speed nonconductors and brushes to create the static electricity. They can provide extremely high voltages, but since the current or amperage is very low, they are still safe to use.
Shock others with your knowledge of science
Resources
The following resources provide information on this subject:
Websites
Edmund Scientific Company - Sells the Wimshurst Electrostatic Generator for about $180 and the Van de Graaff Generator from $165 to $425, depending on its size.
Electrostatic Machines - An excellent resource from by Antonio Carlos M. de Queiroz of Brazil with information and references on making and using the various types of static electric generators.
Books
Top-rated books on Static Electricity
Top-rated books on Static Electricity
Mini-quiz to check your understanding
1. What can be used to store static electricity?
2. When can high voltages be relatively safe?
3. What factor helps the Van de Graaff generator to create more static electricity?
If you got all three correct, you are on your way to becoming a Champion in Physical Science. If you had problems, you had better look over the material again.
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Generating Static Electricity