Hot Cathode. First the ballast rectifies the AC power, then it chops it to make a high frequency for improved efficiency.
In a gas there are also free electrons "jumping" their way from the negative electrode to the positive at the other side. An electric current stimulates mercury atoms, which causes them to release ultraviolet photons.
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John Miller. An ionized gas is called a plasma.
AC power is good for the lamp because if the lamp was DC, the cathode side would be brighter and more intense since there are more free electrons spewing off of the tungsten electrode there. As a result, they are all made differently, which leads to inconsistent bulb performance.
Common uses: Since we use AC the electrons or ions break off one side, reach the other, then on the next cycle are sent back. This would cause the lamp to overheat and burn out in a span of one second.How Does a Choke Ballast Work?
Berlin, Germany. The resistor is not acceptable for larger power lamps because it creates a lot of waste heat and therefore reduces efficiency.
This is another reason we generally recommend buying a complete lighting system. Cold Cathode.
Give us feedback on this and other pages using our Facebook Page. Search Search the site... The Schenectady Museum. We saw in the last section that gases don't conduct electricity in the same way as solids.