# Electric Flow in a Vacuum

by Ron Kurtus (12 November 2019)

Electric charges, such as electrons and negative ions, will readily flow in a vacuum or near-vacuum as a form of electricity, if there are positive electric charges to attract the particles. Likewise, positive ions will flow if there are negative electric charges to attract the particles.

As the number of atoms or molecules increase in the space between the electric charges, the resistance to electric flow increases.

The most common place that you experience the flow of electric charges in a near-vacuum is in an old-style television picture tube or cathode ray tube (CRT). To a degree, this type of electric flow is also seen in a fluorescent lamp. The Sun gives off streams of charged particles that—when attracted to the Earth's magnetic poles—create the Northern and Southern lights.

Questions you may have include:

• How do electrons flow in a cathode ray tube?
• How do electrons flow in a fluorescent lamp?
• What happens in solar flares?

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

## Cathode ray tube

A cathode ray tube (CRT) has most of its air removed. A filament that is heated white hot gives off electrons. A negative charge is also applied to the filament or cathode to accelerate the electrons away from it. At the other end of the neck of the CRT is a series of plates that are given a positive electric charge. This accelerates the electrons toward it. The plates are called anodes.

Variations in their charges can direct the beam of high speed electrons, as they move past and smash into the television or CRT screen, resulting in flashes of light.

The beam of electrons is called a cathode ray, a name given years ago when the phenomenon was discovered.

## Fluorescent lamps

A fluorescent lamp is a tube where the air has been removed and replaced with a small amount of an inert gas such as Xenon, along with a trace of Mercury. The pressure inside the lamp is about 0.3% of atmospheric pressure, so it is essentially a partial vacuum.

The ballast or cathode heats and ejects electrons which travel toward the anode or positive charged terminal. Upon hitting the gas atoms, ultraviolet radiation is emitted.

## Solar flares

Storms on the surface of the Sun give off streams of electrically charged particles. These electrons and ions speed across the vacuum of space until the reach the Earth's atmosphere. The electrically charged particles are attracted to the magnetic north and south poles. Collisions with air molecules results in lights that can be seen across the sky over the poles.

## Summary

Electrically charged particles will flow in a vacuum or near-vacuum as a form of electricity, if there are electric charges that attract the particles.

A common device to experience the flow of electric charges in a near-vacuum is in an old-style television picture tube or cathode ray tube (CRT). To a degree, this type of electric flow is also seen in a fluorescent lamp. The Sun gives off streams of charged particles that—when attracted to the Earth's magnetic poles—create the Northern and Southern lights.

Seek to understand the principles

## Resources and references

Ron Kurtus' Credentials

### Websites

DC and AC Electricity Resources

Physics Resources

### Books

(Notice: The School for Champions may earn commissions from book purchases)

Teach Yourself Electricity and Electronics by Stan Gibilisco; McGraw-Hill; (2001) \$34.95 - Guide for professionals, hobbyists and technicians desiring to learn AC and DC circuits

## Students and researchers

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

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