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# Static Electricity Sparks

by Ron Kurtus (revised 11 January 2015)

A static electricity spark is an electrostatic discharge (ESD) or sudden flow of electric current across an air gap, heating the air to high enough temperatures to cause it to glow.

The size of the spark depends on the separation of the sources of electrical charges and their potential difference in voltage.

A spark may be only a few millimeters, several meters or even kilometers in length. The amount of heat and noise created depend on the size of the spark.

Questions you may have include:

• What is a small spark?
• How is a medium size static spark created?
• What are the largest sparks?

This lesson will answer those questions. Useful tool: Units Conversion

## Small spark jumps from finger

The most common static electric spark people experience are the small ones that can jump from your finger to some metal object, giving you a slight shock.

Static electric spark jumps from finger to doorknob

Picture from Physics FTW blog

Such sparks really don't cause an electric shock, such as from AC or DC electricity. Instead, they simply shock or startle you. The pain felt is from the heat caused by the electrons jumping the air gap.

The noise made from such a spark is a snapping sound, cause by the rapid heating of the air.

They usually occur when your body builds up static electricity, often due to your dry skin rubbing against your clothing or after walking across a polyester rug.

The amount of voltage required for a 2 millimeter spark from your finger to the doorknob is about 6000 volts. Since the current is very low, there is no real danger from such a high voltage.

Although the spark cannot harm you, there is a danger of such a spark if it occurs when you are near gasoline, such as in a filling station. It could cause a fire or even an explosion.

Reducing Static Electricity Shocks.)

### Large sparks from Van de Graaf generator

A Van de Graaf static electric generator can produce over 400,000 volts of potential energy. This is sufficient to send a spark from the generator globe to another metal sphere over 50 cm or 20 inches away. These generators are often seen in school science labs and are used for experiments and demonstrations.

The simulation below shows how a large Van de Graaf generator can send long sparks across the gap.

Simulation designed by Jim Bumgardner

You can adjust the knobs with your mouse to change the look of these static electricity sparks or mini-lightning bolts.

• 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.

### Lightning

The largest sparks are seen with lighting bolts, which occur during thunderstorms.

Lightning during a storm

A lightning bolt can be over 1.5 km or about 1 mile in length. The amount of voltage released in a lightning bolt is typically about 100,000,000 volts.

The sound of thunder is caused by a shock wave created in the air, similar to the sonic boom of a supersonic jet plane. The lightning occurs first and the thunder occurs a fraction of a second later.

## Summary

A static electricity spark is a sudden flow of electric current across an air gap, heating the air to very high temperatures, cause it to glow. The size of the spark depends on the separation of the sources of electrical charges and their potential difference in voltage. A spark may be only a few millimeters, several meters or even kilometers in length.

Be observant and discover more

## Resources and references

Ron Kurtus' Credentials

### Websites

Humans and Sparks - Preventing painful static sparks

Static Electricity Resources

### Books

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.

## Students and researchers

www.school-for-champions.com/science/
static_sparks.htm

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