Answer / kunal singh dabi

A mains tester works because the potential difference
between the live and Earth makes a very small
(imperceptible) current flow through the tester and our
body to Earth. This current is just enough to light the
lamp / Neon. When you stick it in the Neutral socket, the
potential difference (just a volt or two, usually) is not
enough to give sufficient current to light the neon.When
the tester light glows, it mean electrons flow like,from
live terminal > tester > body > floor & walls of building >
inside the earth>goes back to the generator, via earth or
neutral conductor (Please note that somewhere, Neutral and
Earth are connected together so we have, in effect, a huge
loop of circuit.)

Above description is for AC supply only ( path complete
thorough earth or nutral to generator neutral), however
please note the fhilosophy is not applicable for DC supply
where - V is in floting condition (not grounded or earthed)
so due to un completation of that circuit tester light will
not glow.

Answer / kannan

there is a ballast resistor which is connected in series
with the testing terminal and the neon lamp, this limits
the current flow to the neon lamp, there to body & ground.
this is the one which protect you from electric shock. but
you cannot go on using the tester for any voltage. there is
voltage limitation, normally around few hundred volt, above
which you can get a shock.

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