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.

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