lighting questions

northdublin

hope this is the right place to ask such questions so here goes.
in relation to flouresent lighting why does this type of lighting system along with metal halide and son need gear such as ballasts , ignitors and caps.
we keep all the above and ive breifly looked at a geartray and all that i can come up with is that a ballast looks like some sort of a traffo due to its weight and construction and that the cap is there to smooth out voltage.
can anyone give me a breif explanation as to why these systems are so popular and bearing in mind that any responce should be put forward as if it was for a 10 year old.......ive asked questions on other forums before and got expert answers as if it was directed to another expert

mutabi

Well, I dont wish to fob you off, but I believe http://en.wikipedia.org/wiki/Electrical_ballast should answer all your questions. I could try to put it in my own words, but I reckon this page does an excellent job of defining why we need to use a ballast for fluorescent lights.

If you still have any questions after reading that, let us know!

Andrea B.

Hello Mutabi, it serves two functions.

Firstly it provides the initial high voltage to strike a flow of current across the gas in the lamp, which when excited is able to carry current at 230v.
The strike of high voltage is caused by the starter switching off, which causes the magnetic fields built up around ballast to collapse inwards and hence induce a high voltage to strike across lamp gas.
At this stage, the starter is non functional as we have current flowing through the route of least resistance, the lamp gas.
However, this resistance is so low here that we need a current limiting (hence the sometimes used term for ballast of "choke") device.
The constantly rising and collapsing (50Hz) magnetic fields at the ballast induce back flows of current against the operating current which is a resistance to current flow in the circuit and is known as impedence.

Stoner

http://home.howstuffworks.com/fluorescent-lamp4.htm

not a bad description from start to finish, no point in typing it all out again.