How does a plasma light work?

Answer 1

Plasma lamps (also variously plasma globes, balls, domes, spheres, or orbs) are novelty items which were most popular in the 1980s. The plasma lamp was invented by Nikola Tesla after his experimentation with high frequency currents in an evacuated glass tube for the purpose of studying high voltage phenomena. Tesla called this invention an Inert Gas Discharge Tube.
Plasma lamps are available in different shapes, including spheres, retangular cylinder and cylinders. Although there are many variations, a plasma lamp is usually a clear glass orb, filled with a mixture of various gases at low pressure, and driven by high frequency alternating current at high voltage (approx. 35 kHz, 2-5 kV), generated by a high voltage transformer. A much smaller orb in its center serves as an electrode. Beams or 'snakes' of light (actually emergent patterns in ionized gas) extend from the inner electrode to the outer glass container, giving the appearance of multiple constant beams of colored lightning (see corona discharge and electric glow discharge). The beams initially follow the electric field lines of the dipole, but move upwards due to convection.

Placing a hand near the glass alters the high-frequency electric field, causing a single beam to migrate from the inner ball to the point of contact. An electric current is produced within any conductive object near the orb, as the glass doesn't block the flow of high frequency electrical current. The glass acts as a dielectric in a capacitor formed between the ionized gas and the hand.


[edit] Potential Dangers
One should be careful when placing electronic devices (such as a computer mouse) nearby or upon the plasma lamp: not only may the glass become hot, but the high voltage may place a substantial static charge into the device, even through a protective plastic casing. The radio frequency field produced by plasma lamps can interfere with the operation of touch pads used on laptop computers, digital audio players, and other similar devices. Some types can radiate sufficient RFI to interfere with nearby telephones up to several feet away. If the phone uses electronic dialling then the RFI can add digits to the number being dialled; this can effectively prevent calling. Additionally, when a metal object (such as a coin) is placed on the surface of a plasma lamp's glass, a danger of shock and burning does exist; it is very easy for electricity to be emitted from the lamp if the metal comes in contact or proximity with certain other materials, including human tissue. If a medium-sized lamp is wrapped in grounded metal foil, capacitive coupling can transfer tens of milliamperes to ground through the foil, enough to light a small lamp or give a small arc burn. This is possible because the glass acts as a capacitor dielectric, the inside of the lamp acts as one plate, and any conductive object on the outside acts as the other capacitor plate.

In addition it is possible (although difficult) to cause a minor burn to the finger by hovering the fingertip just above the surface of the glass. This causes a small arc to form and generate heat by simultaneously "optimising" both the voltage across the gap and the current through it.

Answer 2

How Do Plasma Lights Work

Answer 3

Plasma is an ionized gas; light is generated when atoms in the gas change energy state. Gas can be ionized by passing electric current through it, which is the way plasma lights work.