Answer Posted / mohit sharma

A fluorescent light does not have the usual glowing
filament of an incandescent bulb, but instead contains a
mercury vapor that gives off ultraviolet light when
ionized. The ultraviolet light makes particles that coat
the inside of the tube, and these particles glow or
fluoresce (see How Fluorescent Lamps Work for details).

Fluorescent starters are used in several types of
fluorescent lights. The starter is there to help the lamp
light. When voltage is applied to the fluorescent lamp,
here's what happens:


The starter (which is simply a timed switch) allows current
to flow through the filaments at the ends of the tube.
The current causes the starter's contacts to heat up and
open, thus interrupting the flow of current. The tube
lights.
Since the lighted fluorescent tube has a low resistance,
the ballast now serves as a current limiter.
When you turn on a fluorescent tube, the starter is a
closed switch. The filaments at the ends of the tube are
heated by electricity, and they create a cloud of electrons
inside the tube. The fluorescent starter is a time-delay
switch that opens after a second or two. When it opens, the
voltage across the tube allows a stream of electrons to
flow across the tube and ionize the mercury vapor.

Without the starter, a steady stream of electrons is never
created between the two filaments, and the lamp flickers.
Without the ballast, the arc is a short circuit between the
filaments, and this short circuit contains a lot of
current. The current either vaporizes the filaments or
causes the bulb to explode.

PLEASE SEND THE PREVIOUS YEARS QUESTION PAPERS OF RRB JUNIOR ENGINEER-ELECTRICAL

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