Mains Power Electricals :
Mains Power means the 230 V AC 50 Hz or 110 V AC
60 Hz in some countries, The lower power line like 5A is used for small
lamps and fans. The higher power line 15A is used to drive the High
Power Electrical
Appliances like Heaters and Motors. This is a single phase supply. 
Single phase Supply in layman language means a Live, a Neutral and
an optional earth. The earthing is a must in every building along with
lightning protection. The Neutral is a close to earth potential, The
live can give a shock to a man who is in contact with earth at some
part of the human body. So great care has to be taken. This live wire
or point can be
easily checked by a quality standards approved Neon Tester.
Three phase supply - there are three Live wires, used in
factorys and apartments to power bigger loads and Motors. A 3 phase
AC motor is very efficient and economical and most machines like
Drills and Lathes are powered by AC Motors. 3 phase supply
becomes essential for industry.
The voltage is transmitted and supplied to houses at a high level in
comparison to low level of batteries. This High Voltage is not safe but
Inevitable, as transmitting at lower voltage means greater
current carrying requirements of wires and connectors. That leads to
more copper or aluminum usage, more wastage of power due to I2R.
Earthing has to be good, use a Earth Leakage Trip Device. If earth wire
gets snapped outside and some appliance is leaking, the metal clad
appliances may give shock. Even if no appliance is leaking, the current
thru y-capacitors of EMI Filters in Electronic Gadgets like computers
are enough to make your Neon tester glow.
Anantha Narayan
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